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