Color.HSVA
From Xojo Documentation
Shared Method
Returns a Color from hue, saturation, value and an alpha channel. These values are represented by Doubles between 0 and 1. Alpha is an Integer from 0-255.
Notes
The alpha channel is the translucency of the color represented as an integer between 0 (opaque) and 255 (transparent).
Sample Code
Set a color using hue, saturation, value and alpha: