So this is per column, not per cell. Sorry I missed that part of the request.
Having said that, if your cell if a certain number it will only affect that those cells. If you only wanted to make like Cell B20 (like in Excell for example) a certain colour, you couldn't. Unless you made it match a certain criteria: Ex: B20 = 'topics' and test to find topics and you're good.
Happy to help here! If you are looking to conditionally set a column to be red or green based on if it has an 's' or 'b' in it you could use one of two code snippets depending on whether the column will only have an 's' or 'b' in it or if they're full words your checking.