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