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