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