[rcolor] let use hex and plain color name
[rcolor] let use hex and plain color name

RColor will support several formats. Now it is:
 hex - 6 digits like 00FF00 (default now)
 rgb - decimal R,G,B  like 0,255,0
 name - plain SVG name like "white" or "black"
 
For all parameters one could specify alpha - double value between 0 and
1.
 
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