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