A 28-knot Colorado would be a different battleship

Could the Colorado-class battleships be rebuilt for 27 or 28 knots?

Not realistically within the existing design: reaching that speed with 1920s machinery would require changes so extensive that the result would effectively be a different ship.

The answer rejects the idea that additional machinery alone can turn a standard-type battleship into a fast capital ship. A jump from roughly 21 knots to 27 or 28 knots requires far more power and the internal volume to produce and transmit it. With 1920s technology, those demands reshape the hull and the balance between armor, machinery, and displacement. The resulting vessel would stand closer to the design difference between the Royal Sovereign and Renown classes than to a simple Colorado refit.