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