Ordering color sealer quantity depends on how much grout you have.
Generally, a 4 oz bottle will cover 600 square feet of 12 inch tile with 1/4 inch grout line. If tiles are smaller than 12 inch, then the 4 oz bottle will not cover as much area. Likewise larger tiles will allow you to cover a larger area.
Colors render on monitors and cell phones differently. Use for general/approximate reference only. Color swatch cards are the most accurate way to select color and are available at any contractor supplier of tile and grout. (Home Depot, Lowes, etc)