First let's talk about “Brown Out“. This is referring to usually when the electric company might be working on the power grid. You will have the lights flickering and going very dim. That’s why it is called a brown out because the lights are dimer and everything looks somewhat brown. An example is “It looks like there might be a brown out as the electric company works on the power lines.”
The next brown color idiom is “Brown Bag It“. This is usually said as a verb. When a person is going to work or school or anywhere they will be gone long enough to have a lunch, and they bring their lunch instead of buying it, they are considered to be “Brown bagging it”. This color idiom is referring to a usual manner of someone carrying their lunch to work in a brown paper bag.
Another idiom is “Brown Noser” or “Brown Nosing“. This is a somewhat vulgar color idiom because it is referring to someones nose having poop or feces on it. When people are trying to be flattering to their boss, they are considered to be “kissing the butt”. So if someones is “kissing butt” that means their nose is….well you can imagine.
The following brown color idioms are not used or might be used rarely by Americans. Americans only have a few brown color idioms. Some of these are Australian and some British. So I have included these to give you a few more options.
brown as a berry
very brown from the sun; quite suntanned. (*Also: as ~.)
She was out in the sun so much that she became as brown as a berry.
brown someone off
Sl. to make someone angry. (See also browned (off).)
You really brown me off!
brown out
[for the electricity] to diminish in power and dim the lights, causing a brownout. (Something less than a blackout, when there is no power.)
The power kept browning out. The lights started to brown out, and I thought maybe there was a power shortage.
do something up brown
to do something just right or with great effect.(Fixed order.)
Whenever they put on a party, they do it up brown.
He was determined to cause a scandal, and he really did it up brown.
be as brown as a berry (British & Australian)
if someone is as brown as a berry their skin has become much darker because of the effects of the sun
She's as brown as a berry after a month in Greece.
brown-bagging (American informal)
taking your own food, usually in a brown paper bag, to eat in the middle of the day when you are not at home
We've stopped brown-bagging - it's too cold now to eat in the park.
brown-nose (informal)
to try too hard to please someone, especially someone in a position of authority, in a way that other people find unpleasant
The rest of the class were sick of watching him brown-nose.
in a brown study - Being in a brown study means deep in thought, and more often than not, deep in unhappy or depressing thoughts. According to the American Heritage Dictionary, it comes from brown as in a figurative sense of gloomy, and study, which among many other things can mean "a state of mind or mental absorbtion".
Lack of company will soon lead a man into a brown study.