Using color to evoke a specific idea such as nobility is highly subjective, and the term itself could have multiple interpretations.

The most straight forward answer would be the explicitly named Noble Blue, with hex code #697991.

To evoke the idea of outstanding qualities, you might want a bright and highly saturated blue, such as azure: #007FFF

The idea of royalty, high birth, or exalted rank, might demand a darker shade of blue, such as ultramarine: #011F5B

The idea of being chemically inert or inactive, might be conveyed with a lower saturation, such as silver lake: #5D89BA

Somewhat paradoxically, the noble gasses are responsible for some of the more vivid shades of blue you can find, such as neon blue: #4666FF

Again, using color to evoke a specific idea is highly subjective. It may be helpful to consult a color swatch and choose the color that most resonates for you with the idea you are trying to achieve.
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