No. Citric acid is used in many dyes requiring an acid, and in many foods for its sour taste, but it does not color anything. Here is a full description of the properties: https://en.wikipedia.org/wiki/Citric_acid
They are sour
toxic waste sour candy, the sourest candy in the world. I guess it counts for substance too.
Acetic Acid
Oxalis montana
Sour tasting foods are usually acidic. The sour taste in foods comes from acids such as citric acid, malic acid, or acetic acid that stimulate taste receptors on our tongue and trigger a sour sensation.
They will eat certain sour foods, but don't really prefer them. They have been known to eat moderately sour foods, such as yogurt, without a problem, but will not eat lemons or other citrus. They generally stay away from sour drinks.
sour milk
yes
I have never noticed a sour taste in my dairy foods. You are possibly letting it get over date.
Citric Acid
Lemonade or vinegar are examples of foods that have a sour taste.
lemon, lime, vinegar, sour sweets, unripened fruit,
acids
When you taste sour while consuming certain foods or beverages, it is because they contain acids that stimulate taste receptors on your tongue, sending signals to your brain that interpret the sensation as sour.
Some foods include yogurt, cheese, and sour cream
Acids typically have a sour taste. Examples of acidic foods include lemons, vinegar, and sour candies.