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