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