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