Is "a deep red in color" redundant?

Solution 1:

As TRomano observes in a comment beneath the question, the sentences

The arils contain a smaller seed in a juicier pulp which varies from a light pink to a deep red in color.

and

The arils contain a smaller seed in a juicier pulp which varies from light pink to deep red.

convey the same information. The primary difference is that the second wording makes explicit the point that the category of variation being described is color—although most readers are likely to figure this out from the nature of the range markers "light pink" and "deep red."

Having said that, I agree with TRomano (again) that if you want to explicitly identify "color" as the category of variation involved, you might as well do it before identifying the range, not afterward. In that case, if I were copyediting the original sentence, I would be inclined to phrase it as follows:

The arils contain a smaller seed in a juicier pulp whose color may vary from light pink to deep red.

But my preference for that wording is based on considerations of writing style, not of syntactical correctness.