We have a variety of brands, purhcased both locally and at ICES over the years. Chefmaster and Wilton are the most common available at retail here. We've bought penty of Americolor at ICES, mainly because they won't ship a lot of it to Canada. (You can take some over te border for "personal" use.) And acquired freebies too.
If I want a bright Canada Day red, or a true black, or a jewel tone, it's Americolor for me. We have so many reds in different brands, but you hate to throw any of them out ebcause they look nicer for different things like flowers or Santa suits.
My go to leaf color is Wilton Juniper Green. (I like all the pastel colors in the garden set.)
Two rather unique colors I've only seen with Wilton are Winnie the Pooh Gold and Barney Purple (the exact color of our lilac trees).
I have a British color called bamboo (don't remember the brand) which makes a nice beige.
Chefmaster Buckeye Brown comes out a nice wood tone.
it can also make a difference what medium you are coloring. The same color in buttercream, royal, fondant, cookie dough, etc. will look slightly different. Not to mention diferent ingredients: up until very recently, our margarine was very pale to distinguish it from butter.
I love seeing all the different colors! and even better when the selections work well together in the final product.