CREATE TABLE ref_colors (color_description VARCHAR(255), color_code VARCHAR(255)); CREATE TABLE products (color_code VARCHAR(255))
What is the description of the color used by least products?
    
SQL: SELECT t2.color_description FROM products AS t1 JOIN ref_colors AS t2 ON t1.color_code = t2.color_code GROUP BY t2.color_description ORDER BY COUNT(*) LIMIT 1