Oxygen's color depends on its state:
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Gaseous Oxygen: In its gaseous state, oxygen is colorless, odorless, and tasteless. This is because it doesn't absorb any visible light, allowing light to pass through unimpeded. [Source: PubChem, Homework.Study.com]
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Liquid Oxygen: Liquid oxygen exhibits a pale blue color. [Source: PubChem, Quora, ChemistryHall.com]
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Solid Oxygen: Solid oxygen displays various shades of blue, red, and even black-metallic, depending on the specific crystalline structure and conditions. [Source: ChemistryHall.com]
It's important to note that the color we perceive is due to the interaction of light with the oxygen molecules. The gaseous form doesn't interact significantly with visible light, resulting in its colorless appearance. However, in liquid and solid states, the interactions with light change, leading to the observed blue hues. The reference to a greenish hue in the cosmos [Astronomy.com] refers to oxygen's role in auroras, where energized oxygen atoms emit light at specific wavelengths, resulting in a visual effect that may include green. This isn't the inherent color of oxygen itself.
While some sources mention oxygen's color in relation to other contexts (e.g., oxygen in blood, or "Oxygen White" as a paint color), these are not the inherent color of the element oxygen.
