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