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