ColorThemes

This template contains 5 color themes, they are green, cyan, blue(default), gray, black , You can choose green with

\documentclass[green]{elegantbook} %or
\documentclass[color=green]{elegantbook}

If you want to customize the colors, please select nocolor or use color=none and declare the structurecolor, main, second, and third colors in the preamble section as follows:

\definecolor{structurecolor}{RGB}{60,113,183}
\definecolor{main}{RGB}{0,166,82}%
\definecolor{second}{RGB}{255,134,24}%
\definecolor{third}{RGB}{0,174,247}%