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