@peachyneko I'm not the one you asked, but the size of an alpha always depends on the material you use and how tight you knot. It might be a little bigger or smaller for a person that isn't you.
You can calculate how big it will be for you by taking an alpha you have already made and measuring how long a certain amount of rows and columns is. This pattern is 122 knots wide and 197 knots long.
@leoswift you can use any brand you like. You just match the colours by eye. As a help for some brands you can find charts online that help you match the hex codes of colours with the string numbers. Do figure out the hex codes used in this pattern, click 'add a variation'.