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