A "conservation" score is calculated for each position is a protein multiple alignment. Conservation scores are calculated according to the method Valdar, see Valdar and Thornton (2001) and Valdar (2002). SnapGene provides the option to display sequence "conservation" as colored blocks or bars, grayscale blocks or bars, or symbols.
The colors or symbols used for conservation score ranges are as shown in the above legends. You can download SVG vector-based images for each legend via the following links.