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