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