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