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