One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,4)(6,8)(9,10)(11,21)(12,26)(13,20)(14,19)(15,18)(16,23)(17,29)(22,31)(24,32)(25,33)(27,39)(28,34)(30,35)(36,38)(37,40) involution — undirected(9,11,15,25)(10,16,18,32)(12,27,30,22)(13,24,14,23)(17,31,34,39)(19,33,20,21)(26,36,35,40)(28,37,29,38)(2,4)(9,12,13,28,15,30,14,29)(10,17,19,35,18,34,20,26)(11,22,23,37,25,27,24,38)(16,31,21,36,32,39,33,40)(5,6,7,8)(10,18)(16,32)(17,34)(19,20)(21,33)(26,35)(31,39)(36,40)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.