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