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