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