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