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