Why use SVG? SVG graphics are vectors, which means you will be able to make them any size without losing quality or detail.
The barcode isn't showing up or it looks malformed. This script is designed to create a valid barcode SVG file. Unfortunately, some browsers do not support SVG (Internet Explorer) and some just really suck at it (Chrome). I recommend downloading the SVG and viewing it in a normal viewer, like Inkscape.
Display size: The default barcode display size is the optimal size according to the encoding's definition. You can, for example, double this size by setting Size Multiplier to 2.
Color: You can set the colors using words, like "black" or "pink", or by specifying the color in hexadecimal, like "#FFFFFF" or "#CFC".