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