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)(11,18)(12,16)(13,15)(14,19)(17,21)(20,23)(22,24)(25,26)(27,36)(28,32)(29,39)(30,35)(31,34)(33,37)(38,40)(1,3,5,4)(2,6,8,7)(9,11,12,19)(10,14,16,18)(13,20,21,24)(15,22,17,23)(25,27,29,38,30,28,31,37)(26,32,39,33,35,36,34,40)(10,15)(13,21)(14,22)(16,17)(18,23)(20,24)(25,28,30,27)(26,33,35,40)(29,38,31,37)(32,34,36,39)(1,4,5,3)(2,7,8,6)(10,16)(14,18)(15,17)(22,23)(25,29,30,31)(26,34,35,39)(27,37,28,38)(32,33,36,40)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.