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