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