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