Official way to change color is in Waveform Viewer > Edit > Color Preferences
QSPICE waveforms colors limitation - QSPICE - Qorvo Tech Forum
Unofficial way with program to load pre-defined color pattern based on @RDunn work is the link shared by @physicboy in previous post. The exact link to @RDunn Github link is
Color preference for Sch editor and Waveform viewer - QSPICE - Qorvo Tech Forum