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