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