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