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)(12,27,28,39)(13,29,30,20)(15,32,16,21)(18,33,38,24)(23,40,31,37)(26,35,34,36)(1,2)(3,6)(4,8)(5,7)(9,11)(10,17)(12,13)(14,25)(15,26)(16,34)(18,37)(19,22)(20,27)(21,35)(23,24)(28,30)(29,39)(31,33)(32,36)(38,40) involution — undirected(9,12,16,24,14,28,15,33)(10,18,21,39,19,38,32,27)(11,23,26,13,25,31,34,30)(17,29,36,37,22,20,35,40)(1,3,5,4)(2,6,7,8)(10,19)(17,22)(18,38)(20,29)(21,32)(27,39)(35,36)(37,40)(1,4,5,3)(2,6,7,8)(9,13,15,23,14,30,16,31)(10,20,32,37,19,29,21,40)(11,24,34,12,25,33,26,28)(17,18,35,27,22,38,36,39)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.