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