Chevy colorado wont go into 4 low, 4 high works fine but light blinks and does nothing when i try to go into 4 low

The inside light is blinking quickly because the front blinker light is out. I'm afraid that without more info I can't tell you why the lights are out.

The blinking light is telling you that you have a headlight out, if you look the service light should be coming on when the light stops blinking.
Replace the head light and all should be fine.

it could be one of 3 things, it could be a vacuum leak or the vacuum actaulor could be bad they are usually under the battery tray if that don't do it check the vacuum line under the truck for oil in the line if there is it will be the vacuum switch on the top of the transimission.

Hello...

The adjustment screws/nuts should be located either on the top of the headlamp assembly, behind the headlamp assembly, or near the frame rail by the radiator support.

You will have vertical adjustment screws for each independent beam (separate highs and separate lows, but will be same screw if highs and lows are the same bulb). You may also have additional horizontal adjustment screws as well

Park your car on a level ground 30 feet from a wall and measure the height from the ground to the bulb and mark on a wall (do this for highs beams and low beams if the bulbs are separate, if highs and lows are the same bulb, only do it for the lows)

For Low Beams: If the headlights read VOR, then aim the brightest part or cutoff part just below the mark on the wall. If it says VOL or nothing, aim them 2 inches below the mark on the wall.

For High Beams (if separate from low beams): Aim the headlight directly at the line you marked on the wall.

The adjustment screws/nuts should be located either on the top of the headlamp assembly, behind the headlamp assembly, or near the frame rail by the radiator support.

You will have vertical adjustment screws for each independent beam (separate highs and separate lows, but will be same screw if highs and lows are the same bulb). You may also have additional horizontal adjustment screws as well

Park your car on a level ground 30 feet from a wall and measure the height from the ground to the bulb and mark on a wall (do this for highs beams and low beams if the bulbs are separate, if highs and lows are the same bulb, only do it for the lows)

For Low Beams: If the headlights read VOR, then aim the brightest part or cutoff part just below the mark on the wall. If it says VOL or nothing, aim them 2 inches below the mark on the wall.

For High Beams (if separate from low beams): Aim the headlight directly at the line you marked on the wall.

The motor that drives the transfer case is not working it has to be replaced.

well thanks.

Transfer case module causes this, first disconnect battery then wait 1 min reconnect and try 4 high should work till you can get a trained tech to fix.

You pretty much answered yourself here, the switch sounds like it is going bad.

4x4 low function will only engage when vehicle is stopped in neutral with foot on brake. try that