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