Punching up plain carpeting

I've been reading a series of magazines from a nearby sidewalk library, and I noticed that many of the rugs pictured were two-color designs, with one color predominating.

That got me thinking about how to take a solid-color rug, and add yarn to it to make a design. Eventually, I remembered that I have a punch needle (which pushes loops of yarn through a fabric from the back), and I wondered if it could be used on commercially-made carpet.

I tried it on two different carpet remnants. I found with the first one that the carpet backing was too strong to push the needle through; I would need to pre-punch each hole with an awl.

With the second, the needle went through more easily, and I was able to punch in a line of loops all the way down the length in only a few minutes. My hand was tired at the end.

I found that I had to set the needle at almost the longest loop length setting to get the loops to show in the carpet pile. (Longer loops than that would require pulling by hand, and it would probably be better to work from the front with a rug hook.) Putting a loop through every other square of the backing mesh made a line that looks just like a line of paint drips. For a more solid color, I would have to punch every square, and more than one row, and even then the original pile would still be mixed in.