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