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