Palette Index numbers
This page details what colurs are used in each control and the associated palette index numbers.
GButton

The face has three possible colours depending whether the mouse is not-over, over or over-and-pressed.
GDropList

GKnob

GLabel

GOption and GCheckbox

GPanel

GSlider

The thumb has four possible colours depending whether the mouse is not-over, over, over-and-pressed or dragged.
GSlider2D

The thumb has four possible colours depending whether the mouse is not-over, over, over-and-pressed or dragged.
GStick

The stick top has four possible colours depending whether the mouse is not-over, over, over-and-pressed or dragged. The indicator has two colours for selected (14) and not selected (1).
GPassword, GTextField and GTextArea

The scrollbar thumb and buttons both have two colours depending on whether the mouse is not-over or over.