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