$\LaTeX$ Colors

1. \documentclass{standalone}
%Before TikZ stuff!
\usepackage{xcolor}
...
   
2. In $\LaTeX$ code:
   \textcolor{white}{I'm Invisible on paper...}
   In TikZ:
   \draw[color=orange] (P) -- (Q);
\draw[white] (P) circle(1pt);
   
3. Named Colors: dvipsnames
   \documentclass[dvipsnames]{standalone}
\usepackage{xcolor}
   black, blue, brown, cyan, darkgray, gray, green, lightgray, lime, magenta, olive, orange, pink, purple, red, teal, violet, white, yellow.
   More:
   \documentclass[usenames,dvipsnames]{standalone}
\usepackage{xcolor}
   
4. RGB: Red - Green - Blue
   $r,g,b \in [0,1]$ - $R,G,B \in 0,1,2,...,255$:
   \definecolor{blues}{rgb}{0.36, 0.54, 0.66}
\definecolor{happyness}{RGB}{20,100,255}
\textcolor{blues}{text}
\pagecolor{happyness}
   
5. CMYK: Cyan - Magenta - Yellow - blacK
   $c,m,y,k \in [0,1]$
   \definecolor{blues}{cmyk}{0.36, 0.54, 0.66,0.33}
   

6. TiKZ Listing: Fig.tikz.tex. PDF   PNG   SVG   ZIP*   \documentclass[]{standalone} \usepackage{tikz} \begin{document} \begin{tikzpicture} \node [circle, fill=blue, opacity=0.5, minimum size=.4cm] at (0.2cm,0cm) () {}; \node [circle, fill=red, opacity=0.5, minimum size=.4cm] at (0cm,0cm) () {}; \node [circle, fill=green, opacity=0.5, minimum size=.4cm] at (0.1cm,0.2cm) () {}; \node at (0,0) {$T=\T$}; \end{tikzpicture} \end{document}

   
7. Convex combinations of colors: \def\mycolor{blue!30!cyan}
\foreach \n in {1,2,...,\NN}
{
   \tikzmath{\d=3*\n/\NN;}
   %Convex combination of colors
   \tikzmath{\dc=100*\n/\NN;}
   \def\col{blue!\dc!cyan}
   \DrawParallel{-3}{3}{200}{\d}{\col}
}