This was someone's reply to my question about moving pixel art:

An animated gif loops through multiple frames of pixel art. Each
frame is a snapshot of a different moment in time during this llama's
hop. When played in real time, it looks like he's hopping!

Here's the pixel llama in a free online pixel editor where you can see every frame.

Take
some time to see how it's done, try making some changes to see how it
affects his animation. When you're ready to create your own, click
"Create Sprite" in the top right of the piskelapp editor.

If you want make an animation that changing colors:
1) Create the first frame of pixel art
2) Hover over the left preview icon of your frame and click "Duplicate this frame"
3) Change the color on the new frame.

Hope this helps!