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