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