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