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