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