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