Animate between two Expression Color Control colors

[Finn Glink]

Hey!
I have a video with some solid shapes, that animate from one color to another and back a few times. Currently I've simply used the "fill" effects and animated the color parameter. I now want to get some extra control over that by specifying the two fill colors using two "Color Control" effects. 

How would I implement that? Especially the smooth fade between the colors.

Thanks for your input!

[Finn Glink · Accepted solution]

...didn't research properly...

Solution (from Andrei Popa on CreativeCow): 

(put this expression on the "fill" effect)
Col=thisComp.layer("BG").effect("Slider Control")("Slider");
color1=thisComp.layer("SETTINGS").effect("Color 1")("Color");
color2=thisComp.layer("SETTINGS").effect("Color 2")("Color");
linear (Col,0,100,color1,color2)

[Mathias Moehl]

Good that you already found a solution!

If you have iExpressions, it also comes with a linear color link expression, which does not require you to touch any code at all: