Table schema:
CREATE TABLE ref_colors (color_description VARCHAR, color_code VARCHAR); CREATE TABLE products (color_code VARCHAR)

Question: 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