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