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