How do you avoid white chocolate seizing?

You need to use oil based food coloring. I’ve used it with no problems for years.

I've found that adding paramount crystals after adding the coloring agent also helps to keep the chocolate smooth. These are white flakes that can be added to increase the fat content in the chocolate and keep it in its liquid state rather than allowing for excess moisture to promote crystallization and seizing.

You should be able to find them in a candy/chocolate shop, or online.

Good luck!

The reason why white chocolate seizes is due to the melting temperature usually. The milk powder can burn and make it very thick. Mett at 110F or lower with an indirect heat source. Also make sure your white chocolate is fresh and not too old. Chocolates not stored properly, especially those with high milk content like white chocolate, can easily absorb moisture from the air. during storage. Moisture absorption can lead to thickness and melting issues also. Here is the easiest melting recommendations:
https://www.santabarbarachocolate.com/easy-chocolate-tempering/

Dang! I'll get the hang of this eventually.

Anyway, butter contains water; shortening and oil don't. If you want to thin out the chocolate, use shortening if you want it to harden, oil if you want it to be a bit malleable.

There are tons of reputable online resources for powdered, oil-based and paste food colorings if you don't have a baker's/confectioner/s supply store near you. Sugarcraft.com is one that I use regularly.

Ooops. Wrong key. As I was saying. . .

If your chocolate does seize, you can magically return it to a fluid state by adding more liquid. Add boiling water, 1 teaspoon at a time, and stir vigorously after each addition until the chocolate is smooth and of a good consistency for drizzling.

And instead of adding the coloring to the already-melted chocolate, try adding the coloring at the very beginning, before the chocolate begins to melt, to get the cocoa and sugar particles wet. This way, the chocolate doesn't suffer a shock to its system.

There are a lot of long, boring details to consider here, such as what white chocolate is or isn't (it's not chocolate, but an emulsion of 20% cocoa butter, sugar and milk), the difference between "real" white chocolate and imitation white chocolate and their different melting points. All you really need to know is this: Melting white chocolate is one of the few food situations when fake is probably better than real.

Chances are good that if you used real white chocolate and melted it too high and too fast, it seized on its own accord even before you added the food coloring. The fake stuff is less finicky and melts smoother and creamier than the real deal. (Another plus: Because it has less cocoa butter, the imitation stuff has a longer shelf life.) Try using Guittard's Choc-Au-Lait White Chips or Ghirardelli Premium Classic White Baking Chips.

If you insist on using premium white chocolate, melt it very slowly on low heat, monitoring and stirring it constantly, so that it doesn't seize and become grainy.

If it does seize, all is not lost.

do NOT allow the tiniest bit of moisture to come into contact with the chocolate, use oil based colors & flavors, instead of water based ones.

You need a fat based colorant to avoid this problem. The chocolate is seizing because you are adding a small amount of liquid to it. http://www.chocoley.com/chocolatecolorings.htm

Thank you puresugar! I will put your advice to the test and let you know how it works. Thanks again.

As a general rule dry all your utensils well, if water gets in contact with chocolate it becomes moist. Try to get away from those utensils that retain moisture. If using a double boiler don´t allow water touch the boiler, water shouldn´t be boiling. After chocolate is melted do not cover the pot/bowl to prevent condensation on the inside of the pot/bowl as it will cause chocolate to seize. Check out this link to help you smooth seized chocolate: http://www.ehow.com/how_114484_smooth-seized-chocolate.html

Check the ingredients of your white chocolate; some don't have much or any cocoa butter and I've had trouble melting those for incorporating with other ingredients. Always melt white choc very gently; probably not in the microwave. Let it cool a bit to better match the temp of what you are adding. And what kind of food coloring do you you use? And how much (ratio)? If it's water or gel, that might be part of the problem. You could try powdered food color (avail at pastrychefcentral.com)--I heard about this in a cake video from the CIA.