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