Oh the blue spot of Texas - so lonely

My friend Trilla, shared with me her Texas washcloth - and the blue dot on it signifies the Amarillo, the city she and her friend were born in - a nice idea and one that I just might steal use (however, it most likely will be in a different state!).

Her question is, and I, too, am curious - is there an easy way to add just 1 stitch of one color easily? She is being tempted by a Sharpie pen, and since she wrote that I won't divulge her address or phone number to protect her.
Please let us know of a solution in the comments or recommendations. Inquiring minds want to know!
Addendum: For more state dishcloth patterns, go to Free Knitted Dishcloths - special thanks goes to Rhonda, the creator of these state patterns!