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