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)(22,37)(23,36)(24,35)(28,33)(29,34)(32,40)(38,39) involution — undirected(1,3)(2,5)(4,8)(6,7)(9,10,13,16)(11,17,23,28)(12,25,15,18)(14,19,26,29)(20,33,36,30)(21,31,27,34)(22,38,24,32)(35,39,37,40)(9,11,21,35,15,24,14,20,13,23,27,37,12,22,26,36)(10,17,31,39,18,32,19,33,16,28,34,40,25,38,29,30)(3,8)(5,7)(10,16)(17,28)(18,25)(19,29)(30,33)(31,34)(32,38)(39,40) involution — undirected(2,6)(5,7)(9,12,13,15)(10,18,16,25)(11,22,23,24)(14,21,26,27)(17,32,28,38)(19,34,29,31)(20,35,36,37)(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.