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