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