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