Gradients and xfades?

Hello.

I am working on a project with max for the first time and have become stuck. What I am trying to do is set a certain two colours in a jit.pwindow that change using sliders. E.g. I change one half of the window from red to black using a slider, and the other half from green to blue using a different slider. I have being trying to use xfade and gradient to do this, but they seem incompatible with each other. Is there something obvious i'm missing?

Here is the code I have now, hopefully it shows what I am trying to do.

My overall goal here is to link these four windows in a way where they change saturation and colour based on sliders, then link the sliders up to something else that moves them automatically. If i'm going about that a weird way please tell me.