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