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