Which wire is constant power 4 the radio, and which color is when the ignition switch is on, 91 ford f150?

It is here

Need color code for radio wiring - Ford F150 Forum

https://www.f150forum.com > need-color-code-radio-w...
Mar. 10, 2017 - 1997 - 2003 Ford F150 - Need color code for radio wiring - I'm trying to replace factory am/fm cassette stereo in 1999 f-150 with aftermarket cd player and ...
Radio wiring diagram - Community of Ford Truck Fans
Feb. 10, 2016
2015+ Ford Speaker Wiring Diagram - Ford F150 Forum
Jul. 6, 2017
2020 Stereo speaker colors? - Ford F150 Forum
Sep. 10, 2020
Radio wiring diagram - Ford F150 Forum
Mar. 10, 2017
More results from www.f150forum.com

Here too

https://www.scosche.com/media/guides/fd1441.pdf

..

SEE ALSO IF YOU CAN GET HELP AT LINK BELOW
http://www.2carpros.com/makes/ford/f150.htm

You are loosing power to the keep alive memory circuit of the radio. I think you may have a defective ignition starter switch. Also there are two hot wires to the radio, one powers the radio, one holds memory and is called the Keep Alive Memory constant power wire. Here is the wiring colors, pull the radio and check the memory power supply wire.
Radio Constant (keep alive memory) 12V+ Wire: Light Green/Purple wire

1990 Ford F150 Truck Car Radio Wiring Schematic
Car Radio Battery Constant 12v+ Wire: Green/Yellow
Car Radio Accessory Switched 12v+ Wire: Yellow/Black
Car Radio Ground Wire: Red or Black
Car Radio Illumination Wire: Blue/Red
Left Front Speaker Positive Wire (+): Orange/Green
Left Front Speaker Negative Wire (-): Black/White
Right Front Speaker Positive Wire (+): White/Green
Right Front Speaker Negative Wire (-): Black/White
Left Rear Speaker Positive Wire (+): Pink/Green
Left Rear Speaker Negative Wire (-): Pink/Blue
Right Rear Speaker Positive Wire (+): Pink/Blue
Right Rear Speaker Negative Wire (-): Green/Orange

1992 Ford F150 Truck Car Stereo Wire Diagram
Car Radio Battery Constant 12v+ Wire: Green/Yellow
Car Radio Accessory Switched 12v+ Wire: Yellow/Black
Car Radio Ground Wire: Red or Black
Car Radio Illumination Wire: Blue/Red
Left Front Speaker Positive Wire (+): Orange/Green
Left Front Speaker Negative Wire (-): Black/White
Right Front Speaker Positive Wire (+): White/Green
Right Front Speaker Negative Wire (-): Black/White
Left Rear Speaker Positive Wire (+): Pink/Green
Left Rear Speaker Negative Wire (-): Pink/Blue
Right Rear Speaker Positive Wire (+): Pink/Blue
Right Rear Speaker Negative Wire (-): Green/Orange

Usually the ground is black. Power is red, Memory (constant power) is yellow, antenna/amp trigger is blue. Speakers usually have corresponding colors to each one. As an example if one is purple, then the negative wire that goes with it to the same speaker is grey with a purple tracer... I hope I've helped. If so please rate my assistance. Thank you and Happy Holidays.

Easiest way to track speaker wires ( and check if speakers are working ) is to solder a couple of wires to an AA battery , with the stereo out of the dash short the wires from the battery across the pairs of speaker wires, the speakers will " Crackle " when they get power from the battery.
Use a continuity tester to find the power wires , one will have constant power, one will have power only with the key on, one will be for the power aerial. It may have an accessory power for an amp.
Good luck!!

all you need is a test light
turn your ignition off
check all the wires with the light
there is one wire that has power
that's the memory one
then turn the key to the second knot
check for the next one that have power
that's the one that will power up the system

1991 Ford Explorer XLT Radio and Speaker Wire Colors
Pulled out the stock radio and found two plugs on the back of it. One plug had 7 wires (Power, Dimmer, Amp etc.) and one had 8 (Speakers).
7 wire plug (I could see these wires immediately from the plug):
Car Radio Battery Constant 12v+ wire = Light Green w/ Yellow Stripe
Car Radio Ground Wire = Black
Car Radio Accessory Switched 12v+ wire = Yellow w/ Black Stripe
Car Radio Dimmer Wire = Light Blue w/ Red Stripe
Car Radio Illumination Wire = Orange w/ Black Stripe
?? Don't know ?? Red Wire (No power to wire Constant or Accessory)
Car Radio Amp Wire = Blue
8 Wire Plug (Wires were wrapped in a grey outer sleeve, had to cut sleeve to get to wires.):
Right Front:
White w/ Green Stripe (+)
Brown (no stripe) (-)
Right Rear:
Purple w/ White Stripe (+)
Light Blue (no stripe) (-)
Left Front:
Light Green (no stripe) (+)
White w/ Orange Stripe (-)
Left Rear:
Light Blue w/ Black Stripe (+)
Yellow (no stripe) (-)
Speaker Wires (found at the individual speakers in the doors)
Right Front:
White w/ Green Stripe (+)
Green w/ Orange Stripe (-)
Right Rear:
Orange w/ Red Stripe (+)
Black w/ White Stripe (-)
Left Front:
Orange w/ Green Stripe (+)
Blue w/ White Stripe (-)
Left Rear:
Red w/ Green Stripe (+)
Red w/ Blue Stripe (-)

here is the wire colors and what they do. it is from the factory electrical guide.

1991 Ford F150 Truck Car Stereo Wiring Schematic
Car Radio Battery Constant 12v+ Wire: Green/Yellow
Car Radio Accessory Switched 12v+ Wire: Yellow/Black
Car Radio Ground Wire: Red or Black
Car Radio Illumination Wire: Blue/Red
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 (+): Orange/Green
Left Front Speaker Negative Wire (-): Black/White
Right Front Speaker Positive Wire (+): White/Green
Right Front Speaker Negative Wire (-): Black/White
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Pink/Green
Left Rear Speaker Negative Wire (-): Pink/Blue
Right Rear Speaker Positive Wire (+): Pink/Blue
Right Rear Speaker Negative Wire (-): Green/Orange