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