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