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