What are the names of the products with color "red"?
select product_name from products as t1 join ref_colors as t2 on t1.color_code = t2.color_code where t2.color_description = "red"
How many are there?
select count(*) from products as t1 join ref_colors as t2 on t1.color_code = t2.color_code where t2.color_description = "red"
What about for those with characteristic named "hot" instead?
select count(*) from products as t1 join product_characteristics as t2 on t1.product_id = t2.product_id join characteristics as t3 on t2.characteristic_id = t3.characteristic_id where t3.characteristic_name = "hot"