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