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