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