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