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)(25,26,31,29,30,33,28,38)(27,34,35,37,36,32,39,40)(9,11,13,19)(10,14,16,17)(12,20,21,18)(15,23,24,22)(25,27,30,36)(26,32,33,34)(28,39,31,35)(29,40,38,37)(1,3,5,4)(2,6,7,8)(25,28,30,31)(26,29,33,38)(27,35,36,39)(32,37,34,40)(1,4,5,3)(2,6,7,8)(9,12,13,21)(10,15,16,24)(11,18,19,20)(14,22,17,23)(27,36)(32,34)(35,39)(37,40)(10,16)(14,17)(15,24)(22,23)(25,29,31,33,30,38,28,26)(27,37,35,32,36,40,39,34)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.