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