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