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