For me, there is a difference, at least in B4A and B4i.
In B4A and B4i, when you draw with Colors.Transparent or xui.Color_Transparent the background pixels of the canvas parent view are set to transparent.
This is different than Colors.ARGB(0, x, x, x) with Alpha = 0
Drawing any color with Alpha = 0 does nothing.
Only Colors.ARGB(0, 0, 0, 0) or xui.Color_ARGB(0, 0, 0, 0) sets the background pixels to transparent, which is Colors.Transparent or xui.Color_Transparent!
This is not the case in B4J, where you need to use Canvas.ClearRect to set the background to transparent. Drawing with fx.Colors.Transparent or xui.Color_Transparent does nothing.