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