IKEA outdoor table: recovering to the original color
That table was not painted in the sense that you think. You will notice that in both pictures you can see the wood grain. A paint would have provided a complete cover up of the grain. Instead the finish on that table was a transparent wood stain. 

That line from IKEA is built with dark acacia hardwood. This wood is very hard and does not take up wood stain nearly as much as a softer or more open grained wood. If the finish was a water based stain then there is a good possibility that the brushing has simply taken off a good share of the stain on the surface of the wood. With a previous water based finish you may want to consider refinishing it with a semitransparent outdoor water based product. A high quality product (also meaning expensive as well) may be able to restore a uniform color to the table. Some stains of this type will have a manufacturer recommendation of one coat coverage but I have used them with two coat coverage (well dried between coats) and had the color hiding more than semitransparent while yet retaining the look and feel of wood.

If the original finish was an oil based stain then it may be possible to renew the surface by applying a coat of a compatible but similar product. Oil based stains do often tend to penetrate deeper into the grain of the wood than do water based products in my experience.