The best way to learn proper English is to read news report, and watch news on TV. Watching TV shows is a great way to learn casual English, slang words, understand culture reference and humor. If you have already watched these shows then you may recall the words used in the following dialogs.

had a PURPLE stripe on their
flag from 1721 to 1917.
The Big Bang Theory Season 12, Episode 13

Listen, I got to level 25
and reached Purple Lotus Swamp, right?
The Big Bang Theory Season 2, Episode 3

which takes it through a range
of colors. Purple, green, blue.
Breaking Bad Season 4, Episode 4

BERNADETTE: Ooh, look at this
pretty PURPLE robe I just got.
The Big Bang Theory Season 5, Episode 19

Penny meant if he were
a PURPLE leprechaun.
The Big Bang Theory Season 5, Episode 18