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