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