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