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