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