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