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