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