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