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