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