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