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