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