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