[1] Open an MS-DOS window.
[2] Type in " edit " and press enter.
[3] Enter name and desired colours(colours are down the bottom)
[4] Save file into a folder as "filename.txt" (make sure you save it as a .txt file).
[5] Exit DOS.
[6] Open Windows Notepad.
[7] Open the file with your name.
[8] Highlight all of your name.
[9] Copy it (hold ctrl and press c).
[10] Click on the text box where you type your name in in the TetriNET program.
[11] Right click and Go to "PASTE", click on it.
[12] You are finished!

The colours:(i haven't tried all these yet)
Press Ctrl P and while keeping your finger on Ctrl press your desired colour.
RED = T
YELLOW = Y
GREEN = L
NEON GREEN = N
NAVY BLUE = Q
BLUE = E
AQUA = W
CYAN = C
BROWN = P
GRAY = U or O or F or K
PURPLE = S
LIGHT PURPLE = H
CRAP COLOR = R
BLACK = D
BOLD = B
SKIP LINE = J
ITALICS = V
BOX = A or G

Alternatively you can download the TetriNET colour typer, also avaliable in the Downloads section.Hheheeh=)