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