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)(11,16)(12,17)(13,18)(14,15)(19,24)(20,21)(22,23)(25,26,31,28)(27,34,30,32)(29,36,38,33)(35,39,37,40)(1,3,5,8)(2,6,4,7)(25,27,31,30)(26,32,28,34)(29,35,38,37)(33,39,36,40)(10,15)(13,16)(17,23)(21,24)(25,26,31,28)(27,34,30,32)(29,36,38,33)(35,39,37,40)(1,2,5,4)(3,6,8,7)(9,11,14,18)(10,16,15,13)(12,20,22,19)(17,21,23,24)(25,28,31,26)(27,34,30,32)(29,33,38,36)(35,39,37,40)(1,2,5,4)(3,6,8,7)(9,12)(10,17)(11,19)(13,21)(14,22)(15,23)(16,24)(18,20)(25,29,31,38)(26,33,28,36)(27,35,30,37)(32,39,34,40)(1,4,5,2)(3,7,8,6)(9,13,14,16)(10,18,15,11)(12,21,22,24)(17,20,23,19)(25,30,31,27)(26,32,28,34)(29,37,38,35)(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.