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