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