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