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