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