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