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