So glad you asked :)! My watercolor palette is a perpetual work-in-progress and I think it will be fun reviewing it once in a while. As of today, this is what it looks like:

It's a John Pike's palette and I'm quite happy with the number of wells, their size, and the ample mixing area. I rarely use the lid for mixing.  

Okay, the interesting part. Colors, from left to right: 

(Colors in bold larger font are ones I use most. The links are affiliate links and will take you to DickBlick.com. If you buy something, I will get a small percentage for sending you their way. Thanks in advance!) 

Blick Dioxazine Violet.

I put it in there more out of habit than out of need. I pretty much never touch it anymore, but dixazine purple used to always come with my St Petersburg pan watercolors, so I've used it for years.

Winsor & Newton Cobalt Blue.

I use it when I want a slightly lighter and more opaque version ofFrench Ultramarine.  

Winsor & Newton French Ultramarine.

The paint I should probably buy by the bucket. In the absence of buckets, I get the largest tube available (37 ml). And it gets used all the time.  

Utrecht Cobalt Turquoise.

One of those random colors I have and occasionally use. Makes a very delicate violet color when mixed with Quinacridone Red.

Blick Phthalo Blue.

I have a complicated relationship with this one. I love it for giving me nice, transparent darks and brilliant greens, but I hate it for not drying fast enough on the palette and invading every single color while I'm on the move and the palette is not just sitting on a flat surface. It's also a bit of a pain to clean up and it's a staining color (so, don't put it where you think you might need to lift paint later). I am considering either keeping it in a separate container or just bringing a tube when I need it.

Holbein Verditer Blue.

Used occasionally. A semi-opaque, easy-on-the-eye color. Thanks to Tom Schaller for introducing me to this one.  The well next to it holds the remains of American Journey Manganese Blue, which turned out to be kind of dull and very crumbly. Not at all the same thing as Winsor & Newton Manganese Blue.

Daniel Smith Blue Apatite Genuine.

Another random color I use very rarely. Super-granulating, bluish dark gray. I like it, I just don't often paint something that would call for it.

Same goes for

Daniel Smith Indanthrone Blue.

Beautiful, transparent dark blue. Reminds me of writing ink.

Daniel Smith Quinacridone Red .

This is my primary red color. I can warm it up with a yellow or cool it down with a blue. It mixes well with pretty much anything. I tried this color in other brands and it works just as well. Quinacridone Magenta used to be in the well next to this one, but I found it to be a bit redundant. The other well next to it used to hold Daniel Smith Rhodonite Genuine. A pretty color, but it crumbles like crazy when it dries on the palette and I can't say it's essential. I also read somewhere in forums that Rhodonite shifts in color.

Daniel Smith Quinacridone Sienna.

Love it! Apparently, I also need a new tube of it. Again. The color is a nice rusty orange. Transparent, mixes well with most colors on my palette. Not to be confused with DS Quinacridone Burnt Orange, which is actually a rather boring brown.

Maimeri Blu Cadmium Orange.

A basic orange color, semi-opaque. Not used very frequently but is good to have when I need an intense orange. The well next to it is the above-mentioned Daniel Smith Quinacridone Burnt Orange - which is not an orange at all, and I will be scraping it out and throwing it away.

Next one is my primary yellow well.

Currently it's Daniel Smith New Gamboge  but I'm pretty sure there is some Daniel Smith Hansa Yellow on the bottom. Maybe even some Indian Yellow. I'm not very picky there. The blob in the next well is

Maimeri Blu Raw Sienna.

A bit too brown and boring for my taste, so I will be scraping that one out, too. 

Blick Yellow Ochre. 

A good color to have, but not a necessity. Quite opaque and tends to get chalky.

Winsor & Newton Quinacridone Gold.

Another color I buy a lot of. Wonderfully transparent, somewhat greenish yellow. I tried it in other brands, trying to find the same thing but cheaper, and was less than impressed. Winsor & Newton it is.

That's it! I also own a box of St Petersburg (Yarka, White Nights) pan watercolors, with some pans already emptied and refilled with other stuff, for trips and such, when I would not bring my large palette.  

What about you? What are the staples on your palette? 

P.S. For an excellent concise overview of different watercolor brand paints, check out this Wonderstreet article.