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