Clarke Griffin played by Eliza Taylor

Bellamy Blake played by Bob Morley

Octavia Blake played by Marie Avgeropoulos

Finn played by Thomas McDonell

Murphy played by Richard Harmon

Monty played by Christopher Larkin

Jasper played by Devon Bostick

Raven Reyes Played by Lindsey Morgan

Abby Griffin played by Paige Turco

Marcus played by Henry Ian Cusick

Wells played by Eli Goree

Chancellor Jaha played by Isaiah Washington

Jake Griffin (or Clarke's dad) played by Chris Browning

These are how they look in the show, so it's no different in the book. Of course, you can imaging them how you want, this is just how they look in the show.