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