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