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