Ok, try this then...
Use only one layer for your main cat photo.
Then on each new frame, as many as you need to create the number of colour changes you want, ad a HUE&SAT Adjustment Layer above the photo layer.
When you add a new frame, change the HUE setting in the adjustment layer to the new colour you want.
Given the fact that Adjustment layers do not add anything to the file size of your document, it may help in creating the animation at a much smaller file size also.
Can't hurt to try it! [righton]
PS: the only thing you'll need to take note of here is that by fading from one colour to the next, you're essentially adding a large number of intermitant frames to the animation. Try to keep this effect to a minimum if you want the smallest file size.

:B