|GIF like this|
2. Duplicate your image.
3. On second layer, click Image > Adjustments > Desaturate
5. Save the layer. Then, undo step 4 and erase the next part you want to be colored, save. Repeat the step until you get them each individually colored with their own seperate version of photo.
1. Open all image saved just now.
2. Drag the second till the last photo into the first image so, the first image will be the first layer.
3. Now click Window > Animation. On the right side of the animation bar, there should be an arrow with some lines. Click on that and click Make Frames From Layers. This will make a gif featuring each layer.
5. How to save the gif ? Click File > Save for Web & Devices... click OK.
Another method which is simpler... ?