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