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