Parameters Properties

The parameter properties will pop-up to the right of the Thea tool window when then user clicks on a layer property.
Color: Use the color selector to define the RGB values of the color
Spectrum: Use the color spectrum mode to define the RGB values of the color
Bitmap: You can use tonemapping (gamma, saturation, etc.), change the projection and mix the bitmap with a color
Procedurals: Procedurals have their own customizable settings