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