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