Yes, oxygen is colorless. In its gaseous state, under normal conditions, oxygen is completely transparent and lacks any color.
Oxygen's Appearance in Different States
While gaseous oxygen is colorless, its appearance changes in different phases:
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Gaseous Oxygen (O₂): Colorless, odorless, and tasteless. This is the most common form we encounter. Multiple sources confirm this, including the NOAA CAMEO Chemicals database which states that "Oxygen is a colorless, odorless and tasteless gas." https://cameochemicals.noaa.gov/chemical/8967 Another source, the Center for Science Education, similarly notes that oxygen forms a "colorless" molecule (O₂). https://scied.ucar.edu/learning-zone/air-quality/oxygen
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Liquid and Solid Oxygen: While gaseous oxygen is colorless, liquid and solid oxygen exhibit a pale blue color. This change in color is due to how light interacts differently with oxygen molecules when they are close together (as in a liquid or solid) compared to when they are far apart (as in a gas). https://www.quora.com/As-we-know-oxygen-gas-is-colorless-then-why-its-liquid-and-solid-form-are-blue-in-colour-1
Why the Color Difference?
The colorlessness of gaseous oxygen is related to the energy gap between its highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). The energy required for electronic transitions between these orbitals falls within the invisible region of the electromagnetic spectrum. https://jeeadvancedchemistry.quora.com/Why-is-Oxygen-colourless-if-it-is-paramagnetic
Practical Examples
Many products and descriptions explicitly mention the colorless nature of oxygen. For instance, oxygen connectors are often described as "colorless". https://www.mymesinc.com/product_p/0138.htm https://www.mymesinc.com/product_p/0098clr.htm
