In Japanese there are two types of adjectives; na keiyoushi (な形容詞) and i keyoushi (い形容詞). There are also some adjectives that fall under both categories.
In general I-keiyoushi are adjectives that end in i (い) before they modify a noun. Na-keiyoushi have to end in na (な) before they can modify a noun. You will learn more about the different kinds of adjectives in another lesson.
The Japanese word for colour is iro (色). One thing that may confuse a English speaker is that some colours change when they are used as an adjective.
The colours in Japanese can change into adjectives depending on where they are placed in a sentence. Below are examples of where the colours are not used as an adjective, so you don't need to change them.
My car is red = watashi no kuruma wa aka desu (私の車は赤です)
Fish is black and pink = sakana wa kuro to pinku desu
When you want to add a colour before the object in a sentence (red car) you have to convert it into its adjective form. The following colours get the letter i (い) added to the end to form an adjective. These colours are i keiyoushi.
Red fish = akai sakana (赤い魚)
Blue umbrella = aoi kasa (青い傘)
White shoes = shiroi kutsu (白い靴)
Black flower = kuroi hana (黒い花)
All other colours remain the same except you add the particle no between the colour and the word its modifying. Yellow and brown can be either a i keiyoushi or with the particle no added after them.
Pink house = pinku no ie (ピンクの家)
Yellow pen = kiiroi pen (黄色いペン)
Brown plate = chairo no osara (茶色のお皿)
The word for blue (ao) can also be used to describe green. In Japan, green traffic lights are called ao shingou (青信号). The word midori did not come into place until about 100 years ago. Still today the word ao is used to describe certain things in Japanese (even though they are green).