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