How to make a child stop coloring on the walls?

I have a lil baby brother who is 3 years...and he keeps coloring on the walls or cuboards or tables..everywhere i go i find scribbles of pen or markers i try to hid them all but the house is really bigg! and there are loads of pens pencils markers everywhere and my brother goes to my dads office and gets some pens what cani do how can i teach him to stop?