color = {r=1, g=0, b=0, a=1} -- red, full opacity
color = {r=1} -- the same red, omitting default values
color = {1, 0, 0, 1} -- also the same red
color = {0, 0, 1} -- blue
color = {r=0, g=0.5, b=0, a=0.5} -- half transparency green
color = {} -- full opacity black