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