[xfusionlockx]

I've tried everything I can think of and it's still not working. Does anyone know how to do this?

[hmmmmm]

I made an include for stuff like this: https://forums.alliedmods.net/showthread.php?p=2565348
You can interpolate between 2 colours easily in either RGB or HSV space, although I recommend doing in HSV then converting back to RGB since it's much prettier.
You feed the interpolation function 2 colours and a t value between 0.0 and 1.0, 0.0 would be full first colour and 1.0 would be full second colour. You gradually increase this t value, and it'll give you the colours in between you're looking for.