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