Format B1 with a fill color of Red. That will be the default for any value other than the values that fit your criteria.
Then use this Rule in Conditional Formatting, choosing a fill color of Green:
Whenever that OR statement is TRUE, the cell will be Conditionally Formatted with Green.
Note: In your post you used the word "between" e.g. "between 20 and 25". That means >20 and <25, but does not include 20 or 25. The formula I suggested has equal signs, so it will include your upper and lower bounds for each letter. Remove the equal signs if you don't want them.
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