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