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