WebKit

Here is red text script

function onDraw()
castle.draw.setColor(100, 0, 0)
castle.draw.text("red", 0, -6, 10, "center", "middle")
end

When you take a snapshot in the background the rainbow color still changes

card-Yv_8

Unaccessible text color and RGB text ￼. Play RGB text by @luke609453, free in your browser on Castle.