To print pages of colored alphabet letters, open Microsoft Word or whatever word processor you have. Resize the font to fit a letter to a full page; color it, and then go to File > Print... and go through the dialog box. Once this is done, if you have a properly set-up printer, you should have a printed page-sized colored letter.
Word processors differ slightly in the way they present their settings, but generally they offer the same sorts and use the same icons to indicate them. This guide is intended for Microsoft Word. However, thanks to this similarity in design, it is applicable to many other word processors.
Begin by starting up Word. Then, change the font, its size and its color via the Font section of the Home tab. (On other word processors, this is generally in the toolbar at the top.) After that, type the letter into the document. For formatting purposes, you may wish to center the word by hitting Ctrl-E or by clicking the Center button in the Home tab.
Once this is done, hit Ctrl-P or go to File > Print, and a dialog box appears. Here, you may change settings such as the number of copies, the amount of ink to use and which printer to use. Other than the number of copies, everything should be set perfectly, so hit Print in the bottom right once you are satisfied. Assuming you have a working color printer, this gives you a page with a letter of the alphabet colored as you wish.