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