On a Mazda 626 95 model, in the stero/radio unit what colour wires are positive and negative I have a diagram but they don't tell me witch colour is pos and neg.

1995 Mazda B2300 Pickup Truck Car Stereo Wiring Diagram
Car Radio Battery Constant 12v+ Wire: Green/Purple
Car Radio Accessory Switched 12v+ Wire: Yellow/Black
Car Radio Ground Wire: Black/Light Green
Car Radio Illumination Wire: Light Blue/Red
Car Stereo Dimmer Wire: N/A
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: Blue
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: 6 1/2? Speakers
Car Audio Front Speakers Location: Doors
Left Front Speaker Positive Wire (+): Orange/Light Green
Left Front Speaker Negative Wire (-): Orange/Light Green
Right Front Speaker Positive Wire (+): White/Light Green
Right Front Speaker Negative Wire (-): Dark Green/Orange
Car Audio Rear Speakers Size: 5? x 7? Speakers
Car Audio Rear Speakers Location: Rear Corners
Left Rear Speaker Positive Wire (+): Gray/Light Blue
Left Rear Speaker Negative Wire (-): Tan/Yellow
Right Rear Speaker Positive Wire (+): Orange/Red
Right Rear Speaker Negative Wire (-): Brown/Pink

1994 Mazda Protege Car Stereo Radio Wiring Diagram
Car Radio Constant 12v+ Wire: Blue/Red
Car Radio Switched 12v+ Wire: Blue/White
Car Radio Ground Wire: Chassis
Car Radio Illumination Wire: Red/Black
Car Stereo Dimmer Wire: N/A
Car Stereo Antenna Trigger: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Front Speakers Size: N/A
Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Blue
Left Front Speaker Negative Wire (-): Blue/White
Right Front Speaker Positive Wire (+): Blue/Red
Right Front Speaker Negative Wire (-): Blue/Yellow
Rear Speakers Size: N/A
Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Blue/Red
Left Rear Speaker Negative Wire (-): Blue/Green
Right Rear Speaker Positive Wire (+): Blue/White
Right Rear Speaker Negative Wire (-): Blue/Green

Here are the colours of the factory radio harness and what they do.
1995 Toyota Camry Car Radio Installation Schematic
Car Radio Battery Constant 12v+ Wire: Blue/Yellow
Car Radio Accessory Switched 12v+ Wire: Gray
Car Radio Ground Wire: Brown
Car Radio Illumination Wire: Green
Car Stereo Dimmer Wire: N/A
Car Stereo Power Antenna Trigger Wire: Black/Red
Car Stereo Amp Turn-On Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Car Audio Front Tweeter Size: N/A
Car Audio Front Tweeter Depth: N/A
Car Audio Front Tweeter Location: N/A
Left Front Speaker Positive Wire (+): Pink
Left Front Speaker Negative Wire (-): Purple
Right Front Speaker Positive Wire (+): Light Green
Right Front Speaker Negative Wire (-): Blue
Left Rear Speaker Positive Wire (+): Black
Left Rear Speaker Negative Wire (-): Yellow
Right Rear Speaker Positive Wire (+): Red
Right Rear Speaker Negative Wire (-): White

2011 Mazda 3 Car Stereo Wire Harness Color Codes
Car Radio Battery Constant 12v+ Wire: Brown
Car Radio Accessory Switched 12v+ Wire: Light Blue
Car Radio Ground Wire: Black
Car Radio Illumination Wire: Light Green
Car Stereo Antenna Trigger Wire: Black
Car Stereo Amp Trigger Wire: Light Blue
Car Stereo Amplifier Location: Under the Passenger Seat
Left Front Speaker Positive Wire (+): White/Yellow
Left Front Speaker Negative Wire (-): Blue/Green
Right Front Speaker Positive Wire (+): Red/Blue
Right Front Speaker Negative Wire (-): Red/White
Left Rear Speaker Positive Wire (+): White/Light Green
Left Rear Speaker Negative Wire (-): Pink/Brown
Right Rear Speaker Positive Wire (+): Light Blue/Brown
Right Rear Speaker Negative Wire (-): Light Green/Light Blue

This model is also called Nissan Frontier2001-2004 Nissan Frontier (North America) Nissan D22 Navara (Australia).

Then, check this:
2004 Nissan Frontier Truck Car Radio Stereo Audio Wiring DiagramCar Radio Battery Constant 12v+ Wire: PinkCar Radio Accessory Switched 12v+ Wire: BlueCar Radio Ground Wire: GrayCar Radio Illumination Wire: Red/BlueCar Stereo Dimmer Wire: Red/YellowCar Stereo Antenna Trigger: N/ACar Stereo Amp Trigger Wire: N/ACar Stereo Amplifier Location: N/ACar Audio Front Speakers Size: N/ACar Audio Front Speakers Location: N/ALeft Front Speaker Positive Wire (+): PinkLeft Front Speaker Negative Wire (-): BlueRight Front Speaker Positive Wire (+): WhiteRight Front Speaker Negative Wire (-): BlackCar Audio Rear Speakers Size: N/ACar Audio Rear Speakers Location: N/ALeft Rear Speaker Positive Wire (+): Light GreenLeft Rear Speaker Negative Wire (-): VioletRight Rear Speaker Positive Wire (+): BlueRight Rear Speaker Negative Wire (-): Pink

Hope this helps.

Car Radio Battery Constant 12v+ Wire: Orange/Light Green
Car Radio Accessory Switched 12v+ Wire: Yellow/Black
Car Radio Ground Wire: Black
Car Radio Illumination Wire: Light Blue/Red
Car Stereo Dimmer Wire: N/A
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: Light Blue
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Orange/Light Green
Left Front Speaker Negative Wire (-): Light Blue/White
Right Front Speaker Positive Wire (+): White/Light Green
Right Front Speaker Negative Wire (-): Green/Orange
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Gray/Blue
Left Rear Speaker Negative Wire (-): Brown/Yellow
Right Rear Speaker Positive Wire (+): Black/Violet
Right Rear Speaker Negative Wire (-): Orange/Violet

Car Radio Constant 12v+ Wire: Blue/Yellow
Car Radio Switched 12v+ Wire: Gray
Car Radio Ground Wire: Brown
Car Radio Illumination Wire: Green
Car Stereo Dimmer Wire: N/A
Car Stereo Antenna Trigger: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Pink
Left Front Speaker Negative Wire (-): Violet
Right Front Speaker Positive Wire (+): Light Green
Right Front Speaker Negative Wire (-): Blue
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Black
Left Rear Speaker Negative Wire (-): Yellow
Right Rear Speaker Positive Wire (+): Red
Right Rear Speaker Negative Wire (-): White

Here is the diagram in words as found at

http://www.modifiedlife.com/2001-mazda-millenia-car-stereo-wiring-diagram/

Car Radio Battery Constant 12v+ Wire: Red/Black
Car Radio Accessory Switched 12v+ Wire: Blue
Car Radio Ground Wire: Black
Car Radio Illumination Wire: Green/White
Car Stereo Dimmer Wire: N/A
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: 5 1/4′
Car Audio Front Speakers Location: Doors
Left Front Speaker Positive Wire (+): Yellow
Left Front Speaker Negative Wire (-): Blue
Right Front Speaker Positive Wire (+): Pink
Right Front Speaker Negative Wire (-): Purple
Car Audio Rear Speakers Size: 6′ x 9′
Car Audio Rear Speakers Location: Rear Deck
Left Rear Speaker Positive Wire (+): Green
Left Rear Speaker Negative Wire (-): Yellow/Green
Right Rear Speaker Positive Wire (+): Green/Black
Right Rear Speaker Negative Wire (-): Green/Orange

Please rate this info.
1994 Ford Explorer Car Stereo Wiring Diagram
Car Radio Battery Constant 12v+ Wire: Light Green/Yellow
Car Radio Accessory Switched 12v+ Wire: Yellow/Black
Car Radio Ground Wire: Red or Black
Car Radio Illumination Wire: Orange/Black
Car Stereo Dimmer Wire: Light Blue/Red
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: Blue
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Orange/Light Green
Left Front Speaker Negative Wire (-): Light Blue/White
Right Front Speaker Positive Wire (+): White/Light Green
Right Front Speaker Negative Wire (-): Pink/Light Green
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Pink/Light Green
Left Rear Speaker Negative Wire (-): Tan/Yellow
Right Rear Speaker Positive Wire (+): Orange/Red
Right Rear Speaker Negative Wire (-): Black/White

1990 Mazda 626 Car Stereo Wiring Diagram
Car Radio Battery Constant 12v+ Wire: Blue/Red
Car Radio Accessory Switched 12v+ Wire: Blue/White
Car Radio Ground Wire: N/A
Car Radio Illumination Wire: Red/Black
Car Stereo Dimmer Wire: N/A
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: 4′
Car Audio Front Speakers Location: Dash
Left Front Speaker Positive Wire (+): Blue
Left Front Speaker Negative Wire (-): Blue/White
Right Front Speaker Positive Wire (+): Blue/Red
Right Front Speaker Negative Wire (-): Blue/Yellow
Car Audio Rear Speakers Size: 6 1/2′
Car Audio Rear Speakers Location: Side Shelves
Left Rear Speaker Positive Wire (+): Blue/Red
Left Rear Speaker Negative Wire (-): Blue/Green
Right Rear Speaker Positive Wire (+): Blue/White
Right Rear Speaker Negative Wire (-): Blue/Green