rgb
Builds a color from 0..255 channel values; a defaults to fully opaque.
Each channel is masked to its low 8 bits before packing, so an out-of-range value wraps rather than throws.
Return
The packed ShapeColor.
Parameters
r
The red channel, 0..255.
g
The green channel, 0..255.
b
The blue channel, 0..255.
a
The alpha channel, 0..255; 0xFF (opaque) by default.