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