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