The green is the color of bile which usually accompanies gastric acid. Acid in its original context referred to a bitter taste. Bitter tasting compounds, such as vinegar, is what led to the modern chemical definition. The chemical definition is less likely to have influenced the populace than the experience associated the somewhat bitter, acidic, taste of gastric acid accompanied by bile.
color - Why are acids usually depicted in fiction as green? - Chemistry ...
Acids themselves don't have a specific color; they can appear in various colors depending on their concentration, type, and form. However, acids can cause color changes in indicators, which helps ...
The color of acid can vary depending on its specific type and concentration. In general, acids themselves do not have a specific color.
This explanation is true for most organic indicators. Litmus is a complex mixture of organic molecules. The molecule responsible for the color change (the chromophore), is 7-hydroxyphenoxazone (image taken from Wikipedia, public domain): See that $\ce {OH}$ group at the lower left? That's where the so-called "acidic proton" is. This molecule is actually a weak acid, meaning that in the ...
For example, from Khan Academy an indicator is a weak acid or base that is added to the analyte solution, and it changes color when the equivalence point is reached But one sentence later: Endpoint: refers to the point at which the indicator changes color in an acid-base titration.
Acids and bases are classes of materials that have different properties. Acid-base indicators change color depending on whether they are in acids or bases. Blueberries contain a substance called ...
Science Daily: Turning a porous material's color on and off with acid