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