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