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