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