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