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)(11,17)(12,15)(13,16)(14,19)(18,23)(20,22)(21,24)(25,26)(27,31)(28,35)(29,39)(30,34)(32,38)(33,36)(37,40) involution — undirected(9,11,13,19)(10,14,16,17)(12,18,20,24)(15,21,22,23)(25,26,30,34)(27,36,37,29)(28,32,38,35)(31,39,40,33)(1,3,5,4)(2,6,7,8)(9,12,13,20)(10,15,16,22)(11,18,19,24)(14,21,17,23)(25,27,28,33,30,37,38,39)(26,31,35,36,34,40,32,29)(10,16)(14,17)(15,22)(21,23)(25,28,30,38)(26,32,34,35)(27,33,37,39)(29,40,36,31)(1,4,5,3)(2,6,7,8)(11,19)(14,17)(18,24)(21,23)(25,29,38,40,30,36,28,31)(26,33,32,27,34,39,35,37)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.