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