3 weeks post laser tattoo removal and now my tattoo has changed color. Is that normal? (Photo)

Based on your picture it looks like you are seeing a slight reduction in the ink from the tattoo. This is a very good sign as the tattoo is starting to break up the original tattoo. Continue to give it some time for your body to continue to heal and then return for another treatment to continue working towards getting it completely removed

It looks like you are seeing a reduction in ink on the shaded areas. It is probably getting broken down and getting metabolized. I would wait for 8-10 weeks before considering re-treatment. 
Good Picture!
Best Wishes

Your tattoo ink’s saturation is lessen, indicating the the metabolizing process of broken tattoo ink pigments.  Laser removes tattoo by breaking up ink pigments from the skin, releasing it into the bloodstream to be flushed out by the immune system through the liver within 8-10 weeks.  The number of treatment is depending on various factors (cover up vs complete removal, laser technology, physician's experience, tattoo size, ink saturation, colors, overall health, skin type, tattoo location, etc.).  Black and gray tats are the most common and easiest to remove with laser. Unfortunately, white ink is quite impossible to get rid of.  As always, seek laser tattoo removal treatment from a reputable professional healthcare provider in your area who is specialized in tattoos removal using PICO laser technology. 

Thank you for your excellent question.
Color changes during removal are common and expected. This is almost guaranteed from titanium dioxide white, which oxidizes to a brown/tan color on its way out. 
That is an excellent result. It’s goong away! Complete removal is highly probable if you keep with your treatments.
Good luck!