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