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