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