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