Well hopefully this will help.

This is how I’ve colored GIFs and I’m not doubting there are easier ways, but this works for me.

I use Photoshop CS5. I’m pretty sure GIMP would work, too. But I’m not too familiar with the program so don’t take my word on it.

______ STEP ONE ______

Make or find a GIF you would like to color.

Because there isn’t much movement in the background or anything, I made it stationary.

This will help to keep the final GIF under 500kb as well as make it easier to color the background.

This is the tutorial I used to learn that myself.

______ STEP TWO ______

Add a new new layer for each frame of your GIF.
Make it so each for each frame the desired new layer and base layer (the one with the actual picture) appear.

These new layers will be where you add the color, so set the mode on each layer to Color.

______ STEP THREE ______

Open a picture(s) you want to get your colors from. For these Extraordinary Merry Christmas Christmas Special scenes, I like to use this picture:

pretty much because it has all the colors you could actually need, like skin, lips, hair, & clothes.
And I’ll be using this picture a bit for the background.

______ STEP FOUR ______

Select the Eyedropper Tool and find the color you want.

I, personally, like to start with the skin, but you can obviously start with anything you want.

______ STEP FIVE ______

Select the Brush Tool and START COLORING!

If you don’t think the color looks quite right, adjust it until it does.
REPEAT STEP FIVE ON EACH LAYER. This way you still have the color you selected. Keep in mind you may need to change the size of the brush for the smaller areas.

If you do end up changing the color on accident, DON’T FRET! To re-select the exact color, simply change the mode on the layer to Normal and use the Eyedropper Tool to choose the color again. 

Because I often work on multiple things at the same time, I just create a completely new layer above all the others, that I use as a ‘Color Resource’. And only make it visible when I need to select a color.

This can come in handy if you need to make touch-ups a lot, too, like I do.

______ STEP SIX ______

Repeat steps 4 & 5 until you have the entire person(s) colored to your liking.

______ STEP SEVEN ______

Create a New Layer under all the layers you’ve just added. You will use this layer to color the background.

And don’t forget to change the mode to Color.

IF YOU DIDN’T MAKE YOUR BACKGROUND STATIONARY:

• You can either just color the background right onto each layer.
• Or add a New Layer for each frame (still under all your previous New Layers that have color on them). Follow step 2 to make sure they appear on the frames you want.

______ STEP EIGHT ______

COLOR YOUR BACKGROUND using steps 4 & 5!

______ STEP NINE ______

Take the time for touch-ups. Even the smallest change can make a huge difference. But also keep in mind that this is a GIF (that is, if you’re making a GIF and not simply coloring a B&W picture) and the frames will always be changing.

______ STEP TEN ______

I guess this doesn’t need it’s own step, but
NOW YOU’RE DONE!

Aaaaand if you just want to reblog this final GIF, you can find it here.