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