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