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