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