Artist's Oils on the plaette won't dry for the whole day, so usually don't need to find ways to store colors being mixed.

But overnight is another question.

Other then put the mixed color into a bottle, are there any other ways to keep them from drying?

P.S. - Book suggest putting the whole plaette inside the freezer, but family won't allow me to do so.

For AV color, you may add Retarder Medium to postpone the drying time but you may better cover it by a bowl or disc to even postpone it longer

Yes, I know for Acrylic paints like AV Color, one could use an wet plaette with lid.

But I am talking about Artist's Oils (油彩), those people use for Oil Plaiting (油畫).