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