By default, URLs and cross-reference links are printed in black in PDF
output. Very occasionally, however, you may want to highlight such
“live” links with a different color, as is commonly done on web
pages. Texinfo provides a PDF-specific option for specifying these
colors, which must be used inside @tex:
@tex
\global\def\linkcolor{1 0 0} % red
\global\def\urlcolor{0 1 0} % green
@end tex
\urlcolor changes the color of @url output (both the
actual URL and any textual label), while \linkcolor changes the
color for cross-references to nodes, etc. They are independent.
The three given values must be numbers between 0 and 1, specifying the amount of red, green, and blue respectively.
These definitions only have an effect when the PDF output is produced
with the pdfTeX program, not with other ways of getting from
Texinfo to PDF (e.g., TeX to DVI to PDF). Consequently, it is ok
to specify this option unconditionally within @tex, as shown
above. It is ignored when DVI is being produced.
We do not recommend colorizing just for fun; unless you have a specific reason to use colors, best to skip it.