This is a very broad question, and it depends on how much of each color is already used. I probably would not introduce a fourth color, if that's what you're asking. Part of the charm of cottage style is that it tends to be simple and the colors muted.

Post a photo of the room with the upholstered pieces and you'll get more specific advice.

The walls are pale beige, the moldings are off-white (alabaster by SW), Plantation shutters are same color as molding. Planning to purchase off -white sofa. Toulon chairs off-white covered in stripe with off- white, coral,apple green, pale yellow with coral dominating. Antique settee has off-white background with coral flowers and apple green stems. Will the white wood pieces be too much white?
The room is in progress, so have no pictures yet. Just trying to plan. Thanks for any help you can give

I would wait on the pieces you haven't purchased till you get in the actual room. Colors will look entirely different depending on lighting, the size of the space, windows, etc. You'll have a much better notion of what you need once the chairs and settee are in place. Choose your sofa, rug, and art at the same time to coordinate the look.