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