"brąz" is bronze. If I wanted to say that something has the color of bronze I would say "ma kolor brązu" or "o kolorze brązu".
On the other hand, if the context is clear, "brązowy" can also mean bronze, as in "she won the bronze medal" - "wygrała brązowy medal".
The phrase "ma kolor brązu" is correct, "o kolorze brązu" is incorrect - but it would be correct to say "w kolorze brązu".
In Polish, it is important not to mix distinct things about colours: there are nouns (as colour names) and adjectives (as properties of objects). When we write about a property of an object, we use adjectives, not the colour names (which are basicly abstract objects). For example: "czerwień" (noun) is purely abstract and is the name of the colour "czerwony" (adjective). The name of the colour "brązowy" (adjective) is the word "brąz" (noun), but this one is not so much abstract, because "brąz" also is name of bronze (metal). You may look into a long and detailed explanation on the bottom of https://www.duolingo.com/comment/16569658
So the correct way of describing colours by adjectives would be:
- (an object) jest brązowy/brązowa/brązowe [an object is brown] - most natural and neutral phrase
- (an object) ma kolor brązowy [an object has the brown colour] - also natural and neutral phrase
- (an object) o brązowym kolorze (+ verb) - [an object, which is brown + verb] - the whole phrase "rzecz o brązowym kolorze" can be the Subject in a sentence, but rarely would be found outside of full sentence. It is a bit sophisticated, or can be used if you cannot say what is the thing you are talking about, you may describe it by its colour: e.g. Coś widzę, jakąś rzecz o brązowym kolorze. - [I can see something, a thing which is brown].
But you have more choices. If you want to use noun, you can do it. With colour names that are abstract (czerwień) - this is not so complicated:
- (an object) jest (cały) w czerwieni - [an object is (all) red]
- (an object) jest w czerwieniach (plural) - [an object is in reds; an object is coloured in shades of red]
It is different for nouns that are not purely abstract (brąz) - there are more options:
- (an object) jest w brązie - [an object is in bronze / in brown] - this has double meaning: may be understud that something is brown, but also that is made of bronze (metal).
- (an object) jest w brązach - [an object is is coloured in shades of brown]
- (an object) jest z brązu - [an object is made of bronze]
- (an object) ma kolor brązu [an object has the same colour as bronze (metal)] - a comparative figure
- (an object) jest w kolorze brązu - [an object is of the same colour as bronze (metal)] - also a comparative figure like the previous
Would it be fine to say? Our bike is brown. As nickname for motorcycle
Are there times when using either "motor" or using "motocykl" are more common or more appropriate? Such as, a style of motorcycle?