Delete repeated word in text file

Hi expert,
I am using C shell. And i trying to delete repeated word.

Example file.txt:

BLUE
YELLOW
RED
VIOLET
RED
RED
BLUE
WHITE
YELLOW
BLACK

and i wan store the output into a new file:

BLUE
YELLOW
RED
VIOLET
WHILE
BLACK

I have no idea to write the script about it.

Thks for help =)
CHEERS

using AWK:

awk '!x[$0]++' file.txt > newfile.txt
sort -u infile >>newfile

that would change the order of the lines

Whiteboard ans is worked.
But I duno why Yogesh ans cant worked.
anyway, Thks for ur help =)

Its working fine for me...

$ cat file
BLUE
YELLOW
RED
VIOLET
RED
RED
BLUE
WHITE
YELLOW
BLACK
 
$ awk '!x[$0]++' file
BLUE
YELLOW
RED
VIOLET
WHITE
BLACK

Are you getting any errors??? post your output

Output is :-

[$0]++' file Event not found

Why ah?