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