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