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