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