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