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