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