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