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