Hope that helps - I know it is kind of a subjective way to tell. Mixed Gas Bottle 30/70. Take 2 brown paper bags, pour straight gas on one and the other with mix or supposed to be mixed on the other. Color Coding Explanation Color-coding is used as a gas identifier worldwide for medical gas fittings and connections. Most of the people think that there is only one color of the gasoline, but they are wrong. Hope that helps - I know it is kind of a subjective way to tell. But if you didn’t know already there are at least three different blends of mixed gas used in the cellar. The gas cylinder colour code system is designed to provide an instant visual cue identifying the contents for practical and safety reasons. How to tell if oil is in gas, try this. Normal gas is more yellowish. Now, it is only up to you to find the right gasoline and pour it into your car. Is it possible to use the wrong gas in your cellar? The 2 Cycle gas should have a bluish color to it from the oil which is mixed in. The following color-coding chart is for your assistance. Here in this review, you can find out everything about what color is gasoline and the quality of the fuel in general as well. Gas Cylinder Colour Code Chart The gas cylinder colour code is indicative of the gas contained in the cylinder. No you say there are different fittings for Co2 and mixed gasses.