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