This would require you to update the multi-selection for each individual item (Over 1000)
Wouldn't be better creating some sort of Global association of colors?
White:[“white”,”bone”,”cream”,”beige”,”Arctic White”,”Blizard”,”Polar”]
[“white”,”bone”,”cream”,”beige”,”Arctic White”,”Blizard”,”Polar”]
Black:[“midnight”, “Ebony”, “Graphite”,”Charcoal”] [“midnight”, “Ebony”, “Graphite”,”Charcoal”]
As you get new colors you add them to your array OR a table in your database.
Since it's global it should probably be some sort of Admin Custom Table - Probably in the same menu as:
Catalog -> [Products, Categories, Attributes,Colors]