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