So the above comment works for Construct 2, but it didn't work for me for Construct 3.
I did some digging in the forums and actually found a solution:
If the link above is no longer active for whatever reason, here's an abridged version of the solution:
"@SteamPoweredPix Hi, I was having the same exact problem - it really seemed as though effects that require color parameters were just broken in Construct 3, but they're not! Here's how pass color values to effects now.
Instead of the C2-style "parameter 0 = red, parameter 1 = green, parameter 2 = blue", C3 color parameters are just a single value of "rgb" type. To get that you use the System expression "rgb" and pass it three numbers between 0-255 (not 0-100 like in C2).
CODE: SELECT ALL
Solid red:
Set effect "SetColor" parameter 0 to rgb(255, 0, 0)
Solid green:
Set effect "SetColor" parameter 0 to rgb(0, 255, 0)
Solid blue:
Set effect "SetColor" parameter 0 to rgb(0, 0, 255)
Solid grey:
Set effect "SetColor" parameter 0 to rgb(128, 128, 128)
And so on. Hope this helps!"
-- Quote is from JerkTheRipper
Thanks!