Flexcolor CQ is Luxury Vinyl Tile Grout; Here is the removal directions from Shaw's technical department for LVT grout;
Dried on Grout Haze Removal for groutable LVT ( use only for Array Grout and not another manufacturer's brand):
- Remove grout haze with water or a solution of ¼ cup (100ml) Bright N Easy Polish Remover or household ammonia, mixed with 1 gallon (3.78L) of water.
- Apply a moderate amount of the solution over a small section and allow it to remain about 30 seconds.
- Use a clean 3M (WHITE) pad to loosen the grout haze. Rinse with fresh water and buff with a soft, dry terry cloth towel.
You can be more aggressive with porcelain from a scratching stand point. Finally all of the different flooring companies are using the same grout marketed under their own brand, in this instance Array, they are all made in the same factory with different labels.