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