Categorizing by color

When introducing a new thematic set of vocabulary, I plan activities which tap into previously learnt vocab. At my level, this includes numbers, size vocab, and colors. One activity which I particularly like is categorizing by color. This can be done with any set of items and is a great review of color words. Long ago I made a 'color mat'- a big poster with a space for each color on it (labeled, of course).
My First Graders have just started the theme 'Ranitas'. Using a collection of small frogs and the color mat, I held up each frog and asked "What color is this frog?". I call on a student to answer- this student then gets to place the frog on the appropriate color. I have gathered over the years enough frogs for everyone to have a turn, with multiple frogs of some colors and some colors having no frogs at all. Once all of the frogs are placed on the color mat, then I ask "How many frogs are red? (blue, yellow, etc)" Colors and numbers have now been practiced with a novel item (frogs) which keeps the interest and motivation high.
Tip: since many items are more than one color (a frog could be both yellow and black), I instruct the class to identify the color that it is the most of. This makes it easier to place the item on the color mat.