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