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