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