Which abbreviation would be used for the color dark blue?

The abbreviation for the color dark blue is represented as "DBL." This choice is clear and follows a standard convention where "D" stands for "dark," and "B" stands for "blue," with the "L" likely implying the color is in its fully saturated form. This usage ensures that it is distinct and easily recognizable in contexts where color distinction is necessary, such as design, fashion, or transportation.

The other abbreviations, while they may seem plausible, do not follow as clear a convention or common usage. For example, "DB" could suggest "dark blue," but it's less specific than "DBL." "Dbl" would typically represent "double," not a color, which can lead to confusion. "DkB" introduces an unconventional abbreviation structure; while it could also suggest "dark blue," it is not widely recognized or utilized compared to "DBL." Therefore, "DBL" is the most unambiguous and standardized choice for denoting dark blue.