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