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