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