Why doesn’t ferrous sulfate appear orange in vinegar?

When I mix ferrous sulfate crystals with water, the solution almost immediately turns orange. However, when I mix ferrous sulfate with vinegar, it doesn’t change colors.

Why is this?

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As Poutnik suggests, water contains a small proportion of dissolved oxygen, about $$\pu{10 mg/L}$$. These $$\ce{O2}$$ molecules oxidize quickly some $$\ce{Fe^{2+}}$$ ions, and produce some $$\ce{Fe^{3+}}$$ ions which have a brownish color when included in aqueous complexes like $$\ce{[Fe(OH)]^{2+}}$$ according to : $$\ce{4 Fe^{2+} + O2 + 2 H2O -> 4 Fe^{3+} + 4 OH^- -> 4 [Fe(OH)]^{2+}}$$In vineggar, or in any acidic solution, the brown complex $$\ce{[Fe(OH)]^{2+}}$$ is not formed, because the oxidation equation is $$\ce{4 Fe^{2+} + O2 + 4 H^+ -> 4 Fe^{3+} + 2 H2O}$$ The ferric ion $$\ce{Fe^{3+}}$$ may be included in a water complex like $$\ce{[Fe(H2O)6]^{3+}}$$, which is not brownish.