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