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)(14,15)(17,18)(19,23)(20,22)(21,24)(25,26,29,30)(27,31,33,34)(28,36,37,32)(35,40,39,38)(9,10,13,11)(12,15,16,14)(17,18,20,22)(19,21,24,23)(26,30)(27,33)(28,37)(38,40)(10,11)(14,15)(19,24)(21,23)(25,26)(27,34)(28,32)(29,30)(31,33)(35,40)(36,37)(38,39) involution — undirected(1,2)(3,5)(4,6)(7,8)(9,11,13,10)(12,15,16,14)(17,19,20,24)(18,21,22,23)(25,27)(26,31)(28,35)(29,33)(30,34)(32,38)(36,40)(37,39)(1,3,4,7)(2,5,6,8)(9,12,13,16)(10,14,11,15)(17,18)(19,21)(20,22)(23,24)(25,28,29,37)(26,32,30,36)(27,35,33,39)(31,38,34,40)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.