Writing colored text on top of a background, how ?

[mulle-nat]

I create a plane, which i fill with a gradient. (the simple gradient, not the one with the half-blocks). So the background channel of each cell should be setup, as far as I understand. Now I want to putstr text "on top" of this, by setting the text and the foreground channel, but leave the background channel untouched. I don't see a function for that ? I can use the stained functions just for text, but then I have no control over the color.

I could probably simulate the effect by putting another plane with transparent background on top of the plane with the gradient, but that seems clumsy.