The Colorify filter remaps all color pixels in the active selection or layer to a chosen color. It preserves the luminosity of the image.
Colorify Settings
There are seven color wells that can be used as pre-defined colors to run against the image. Clicking any of these will change the color in the Custom Color well to match. The color contained in the Custom Color well is the actual used color for the filter. Clicking Custom Color will display a color selection dialog where any arbitrary color can be chosen.