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)(11,20)(12,25)(13,17)(14,28)(15,18)(16,23)(19,29)(21,36)(22,34)(24,35)(26,32)(27,33)(30,37)(31,39)(38,40) involution — undirected(9,11,14,23,15,24,29,39)(10,16,19,20,18,31,28,35)(12,22,26,38,13,21,27,37)(17,30,32,36,25,40,33,34)(2,5)(6,8)(9,12,15,13)(10,17,18,25)(11,21,24,22)(14,27,29,26)(16,30,31,40)(19,33,28,32)(20,34,35,36)(23,38,39,37)(9,13,15,12)(10,17,18,25)(11,22,24,21)(14,26,29,27)(16,30,31,40)(19,33,28,32)(20,34,35,36)(23,37,39,38)(1,3,4,7)(2,6,5,8)(10,18)(16,31)(17,25)(19,28)(20,35)(30,40)(32,33)(34,36)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.