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