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