WinStudio
This attribute specifies the RGB settings for the extended colors to be used for the backgrounds of forms and components. Ext. Color 0 is the starting color in a gradient pair, and Ext. Color 1 is the ending color. If only a single extended color is wanted, it must be Ext. Color 0.
When using a gradient pair, be aware that you cannot specify Ext. Color 1 until both the Ext. Color Type attribute and the Ext. Color 0 attribute have been set.
NOTE: Using Ext. Color 0 with an alpha setting of 255 has the same result as using the Color attribute by itself. The advantage of using Ext. Color 0 is that you can also use a transparency (alpha) setting with it.
About Setting Form and Component Background Colors
Ext. Color Alpha 0/1 Attribute
Ext. Color - Gradient Direction Attribute