That would be nice. I know that your wish is for it to be a built-in XUI method, and I know you know how to do this. But for those who are unfamiliar with this...
B4X:
Dim bc As BitmapCreator 'Include this standard core library
bc.Initialize(0, 0) 'Zeroes because we don't really need any bits
Dim argb As ARGBColor
bc.ColorToARGB(xui.Color_ARGB(150, 75, 230, 255), argb)
Log(argb.a & TAB & argb.r & TAB & argb.g & TAB & argb.b)