I have had time to research this a bit more deeply and here are some of my findings.
Spanish
Conquistadors dressed similar to the imperial armada people, however no mini fig resembles the spanish naval, or land forces. The Spanish uniforms are characterized with yellow and white (mainly white with yellow trim for infantry, and white/yelow with red trim for artillary. However, some reds were used which slightly resemble the new soldier mini figs. The hats vary from tricorns to the shaco, with bicorn variations used sometimes for officers.
French
The royal french army (prior to revolution) used a combination of white and light blue with tricorns, and bicorns, sorry no unicorns
The Napoleonic/revolutionary army and navy used a darker blue with varying trims from gold, red, and yellow. The hats included shako's, tricorn, and bicorn a possible lego canidate is the bluecoats.
The English
The royal english army used a read coat(of course) with white trim (infantry, officers had other colors.) with tricorns, bicorns, shaco's, and the unicorn (ok.. maybe not, but the grenadiers wore a hat that came to a form of a point on the top). A good candidate is the redcoat mini figs.
The brittish navy wore blue with white or gold trim (gold was for higher ranking officers) with varying hats for the different officers (bicorn, tricorn, and a form of top hat.)
A good candidate is the blue coat mini figs.
I could have gone more in depth into the officers clothing, but i believe that this will sufice. Basically the bluecoat and redcoat are both or a likely and historically correct with the British.