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