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