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