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