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