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