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