The color coding of the system is very important. You must always connect the correct color kegs to the matching colored lines to the same color solvent channel. (Example: Red keg, attached with red lines (gas and solvent), to red solvent channel). This color coding is important to keep the correct solvent in the correct kegs. Once you decide to put say, THF in the red keg, then it will always be in the red keg, red lines and red solvent channel. This is important to keep from cross contaminating your solvents.