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