Typically coloured anthocyanins are detected in aqueous alcoholic solutions by red to blue colour pigmentation. Flavones and flavonols are readily detected in white or pale yellow tissues by the appearance of yellow or red colours when the tissue is exposed to ammonia. In general, solutions containing flavonoids change colour when treated with alkali. Following are some common colour tests for flavonoids:

1. Shinoda’s test: A few milligrams of the flavonoid dissolved in alcohol is treated with magnesium turnings. Concentrated hydrochloric acid is then added in drops. Flavonoids especially flavones, flavonols, and flavanones produce crimson red colours. Chalcones and aurones do not show such colour changes.
2. Treat an aqueous alcoholic solution of the flavonoid with aqueous sodium hydroxide solution. Anthocyanins give blue to violet colours. Flavones and flavonols deepen in colour. Chalcones and aurones show red to purple colours. Flavonones give nearly colourless to yellow solutions, which turn deep red on heating (due to isomerization to corresponding chalcones). Isoflavones give brown solutions in visible light or exhibit brilliant blue colours in UV light.
3. An aqueous alcoholic solution of the flavonoid when treated with dilute sulphuric acid gives intensely yellow or orange solutions in the case of anthocuanins, flavones, and flavonols. Flavonones give orange to crimson colours. Chalcones and aurones give deeply red, crimson or magenta colours.
4. All flavonoids in solution when treated with aqueous solutions of ferric chloride give colours ranging from green, purple, to brown.
5. To an aqueous alcoholic solution of the flavonoid, add a few ml of lead acetate solution. Flavones give yellow to deep red-coloured precipitate and chalcones and aurones show deep orange red colours.
6. Solutions of flavonoids either in water or alcoholic solvents, post acid hydrolysis, show typical absorption maxima. Anthocyanins exhibit visible maxima between 515–545 nm. Flavones show spectral maxima at 330–350 nm, flavonols at 350–386 nm, chalcones and aurones at 370–410 nm, flavonones exhibit different spectral properties with peaks at 225, 288, and 300 nms.