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