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