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