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