Thai basil problem

Hello! I am a relatively new gardener and I have a question about my "Siam Queen" Thai basil plant. When I bought it the leaves were green. About a week or so after planting, a lot of leaves on the plant developed a partial reddish/purplish or plum colored hue. Where I live we have had a lot of rain and maybe a disproportionate amount of sun. I fertilized my garden with aged sheep manure when I planted it almost three weeks ago and I just gave the plants their first side dressings this week with an organic fertilizer (I forget what the three number nutrient designation of the fertilizer is but it's they are all low single digits) I was wondering if anyone could tell me why the leaves are discolored? Thanks! Any help would be much appreciated! Ps. The pictures are taken today and the plant seems to have less discoloration today.

I have only grown green basil but have seen lots of purple basil at Farmers' Markets.

Your basil looks good to me. I think maybe you bought older plants stunted in small pots. They look like they are about to flower. If you want the leaves, snap the tops off to get them to branch and develop more leaves. You do not want flowers, you want the plant to spend its energy on the leaf making. With annuals, flowering can be the beginning of the end. It flowers, goes to seed, and then dies as it spreads its seed.

Before I would buy, I always turned the starter plants upside down to pop them out of their container to make sure they are not full of roots - rootbound. You do not want want an old starter plant. Plus you can see if the roots are healthy looking.

I am thinking the top leaves turn purple (normal) when they are starting to push out blooms. I am not familiar with your Siam Queen and whether it always turns purple when it is flowering or maybe you really have another cultivar.

However on a quick check, I did find some photos of Siam Queen, not all reflect this, but some have the purple leaves as it flowers.
https://www.mashrita.com/product/buy-thai-basil-siam-queen-potted-plant-ocimum-thyrsiflora/

Another thing I found was another cultivar of Ocimum thyrsiflora (which yours is too, Ocimum Thyrsiflora Siam Queen) that has the purple leaves just below the flower.
https://davesgarden.com/guides/pf/showimage/178863/

Hope this helps.

Thank you, Kell. That was very helpful. I'm going to snap off the tops. Under the advice of a friend, I pinched the flowers already a couple of times. I think I caught them early enough but snapping the tips off is something I will try. Thank you again!

They probably will not flourish as a young seedling would do for you. Once the plant decides it is going to seed, you are fighting nature. But you should get some good growth.

Sadly, some nurseries do not pull their older seedlings that really should not be sold. Any annual that looks stressed at all, I would not buy. It is an uphill fight.

Pinching the tips continuously on most annuals will get you a bigger lush plant. When it is time to flower, I stop pinching. But some plants you never want to flower.

Much like coleus, I would buy them in 6 packs or 4 inch pots and immediately in the line at the cashier, I start pinching every single end. Then it will branch to 2. In a week or 2, I then pinch those. I never let my coleus bloom and I would end up with just huge plants that lasted thru the fall.