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