One vertex per element, one color per generator, with an edge from x to x·s.
(2,3)(10,18)(14,24)(19,30)(20,31)(25,34)(26,35)(32,38)(36,39) involution — undirected(1,2,3)(4,5,6,7)(8,10)(9,14)(11,19)(12,20)(13,18)(15,25)(16,26)(17,24)(21,32)(22,30)(23,31)(27,36)(28,34)(29,35)(33,38)(37,39)(8,9,11,15,12,16,21,27,13,17,22,28,23,29,33,37)(10,14,19,25,20,26,32,36,18,24,30,34,31,35,38,39)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.