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