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