\def\redTeX{%
\HINTcolor{fg{1 0 0}}\TeX\HINTendcolor}
\def\note{\HINTcolor{fg{0.5 0.5 0.5}}}
\def\endnote{\HINTendcolor}

This is an example showing the \redTeX\ logo in red color.

\note Note: The red \redTeX\ logo is still red inside this grey note.
\endnote

\bye