I would like to change colors from one car to another.
I have figured out the hue and saturation thing but cant seem to figure out how to change actual colors from one to the other.

I am going to try and upload 2 photos that I am talking about.
This is the car I want to change colors on. Hopefully its the black one (sorry about the size)

And this is the color I would like to use Blue
SO I would like to take the blue from one car and use it on the black car.

My goal is to get it to look as realistic as possible with shadows and such.

Any help is appreciated

I can't give you an "easy" way to do this (there may be an easier way, though).

What I did was create 2 duplicates of the same car, highlighted the middle layer, and selected the car area I wanted to change the color of. Then added a layer mask.

Opened the car with the color I wanted to mimic, and using the eyedropper tool, selected the brightest blue, and the darkest black for foreground and background colors, swapped back to the original car image and applied a bi-lateral gradient that flows vertically with the car, and tried to get the best gradient match possible.

Then on the top duplicate, I kept the selection and applied a second but lighter version of the gradient (this requires personal experimentation for adjustments), changed that layer to overlay, and adjusted the opacity level to suit.

EDIT

Mahlvin just ninja posted me
and his method works
..anyway i post the same this may be useful in some other cases or just to know the alternatives

so many ways to skin the cat

1 )
yes the most simple may be select the car to recolor and use Colors/ hue-saturation to try to get a similar color...is not always possible recreate same color but may work
OR
2)
More complex , but more powerful is Colors/components/ channel mixer , take care there to check "preserve luminosity" box...

OR

3)

then i often use an other method may seems more complex but in pratice i found more intuitive

open both images in the same window
(you open the first as usual, to open the second you use File/open as layer )

then sample (with the eyedropper in the toolbox )the most intense blue (not the darker but for example that just over the front wheel )
now on the image you want recolor select well the body of the car (except wheel glassis..just the coachwork you want recolor
Color menu/desaturate (you have 3 option there..just chose that looking better ) if you do well will desaturate only the car you selected
now create a new transparent layer on top set in color mode, and fill up the selection (selection is commune for all layer ) with that blue with the bucket tool (open the too dialog and chose "fill the whole selection)

This usually do the trick, if the color is not sufficently vivid you may dup again the transparent layer filled with blue, but changing the mode in overlay...(you may also experiment multiply in both cases play with the opacity slider in the layer window to fine tune

i know this looks longer and more complex but is my favorite way to recolor, while i found a bit harder find the optimal setting with the channel mixer...

then maybe someone else may have a even better tip..with gimp are oftenmany different ways to get what you wish

Thank you gimp gods... more questions to come.. I am sure I have a pic for you to grade below i lowered it and tinted windows and played with hue
be kind total newb
I noticed there isn't a lot of people that play with cars on here is there any reasoning for that??

I am having trouble selecting the actual body of the car with out the glass and what not .
Do you use the free select tool or am I missing the boat completely?
I got the car I want to change and the car of which the color I want to use in the same window. Did eyedropper tool. Got the color.
Now on the image you want to recolor "select the body of the car"
thanks a million

The free select tool is used in my method, and is another reason I add the layer mask, so I can "erase" (fuzzy select brush (19) adjusted to proper size, using black foreground to make windows, other areas, etc., transparent).

When it gets down to the shadows, you almost always have to add layers to get those in for vibrancy. (overlay with opacity adjustments works best in this case).

Then PC's methods work equally as well or better in some cases. I just wish the Color select tool had a better algorithm for color ranges, as it is now, its just too black or white. I'd prefer those ranges have a more monochromatic region for selecting than it does.

for selection i usually make a quick& rought selection or with a few shift+click with magic wand (each add to the selection, in case of need ctrl-click subtract ...on that car should suffice) or with the free selector...then i grow the selection of 1 or 2 pixel and i enter in quickmask mode to refine (in quickmask you may use brush and filters to correct the selection )

PS
i saw that a lot of people like virtual mods on cars...maybe a few post here , on deviantart you may found many with same passion

I'm attracted more by Off -Road or even Amphibious car , and more fascinated by vehicle able to climb hills offroad and
run on sand and traverse flooded areas...but i like your car mods

I always color mine funky looking...lol

I would love a car with a leopard print!!!

Missed the reflection in the window.. the car is still blue

Other than that,

-Rob A>