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