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