<red>, <green>, <blue> := h | hh | hhh | hhhh
h := single hexadecimal digits (case insignificant)
Note that h indicates the value scaled in 4 bits, hh the value scaled in 8 bits, hhh the value scaled in 12 bits, and hhhh the value scaled in 16 bits, respectively.
Typical examples are the strings ``rgb:ea/75/52'' and ``rgb:ccc/320/320'', but mixed numbers of hexadecimal digit strings (``rgb:ff/a5/0'' and ``rgb:ccc/32/0'') are also allowed.
For backward compatibility, an older syntax for RGB Device is supported, but its continued use is not encouraged. The syntax is an initial sharp sign character followed by a numeric specification, in one of the following formats:
#RGB (4 bits each)
#RRGGBB (8 bits each)
#RRRGGGBBB (12 bits each)
#RRRRGGGGBBBB (16 bits each)
The R, G, and B represent single hexadecimal digits. When fewer than 16 bits each are specified, they represent the most-significant bits of the value (unlike the ``rgb:'' syntax, in which values are scaled). For example, the string ``#3a7'' is the same as ``#3000a0007000''.