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