"I bought many colored pencils."
VGQ! maybe in 'natural usage' 多い is less for this type of retail purchase, but more for taking inventory/stocking up with goods (from supermarket? or [i'm trying to remember previous lessons] ordering/evaluating food?)
醤油が多いです。 There is a lot of soy sauce. 砂糖が多いです。 There is a lot of sugar. ご飯が多いです。 There is a lot of rice.