# Why are nitrogenous hydrocarbons sometimes colorful?

Alanin and dyes contain nitrogen, is being colorful a special feature in nitrogenous substances?

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To answer your question: in alanine there is almost no chance to make double bond in amine group (e.g. $\ce{=NH}$), but nitrogen group ($\ce{O-N=O}$) has a capability to conjunct with other double bonds (can be also delocalized electrons or pi electrons - e.g., nitrobenzene)