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