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