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