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