The changing colors happen while white blood cells remove the decayed blood products bit by bit.
For the first two days, bruises appear red because of the iron in the leaked blood.
Yellow, on days seven to 10, represents the bilirubin.
Finally, the bruise usually appears brown until it goes away.
Photometric Assessment Of Skin Colour And Lightness Using A Tristimulus Colorimeter: Reliability Of Inter And Intra-Investigator Observations In Healthy Adult Volunteers. Reflectance Spectrometry Of Normal And Bruised Human Skins: Experiments And Modeling.
If authorities can identify this possibility early, further abuse may be prevented.So I have provided an overview of the literature below, with articles split into 2 categories: those that address the attempt to age bruises based on color in a routine clinical environment (Clinical Assessment of Bruises) and those that have a much more high-tech approach (Laboratory Assessment of Bruises). The development of a colorimetric scale as a visual aid for the bruise age determination of bite marks and blunt trauma. These articles address aging bruises using equipment and mathematical models not typically seen in our routine clinical practices. Too many variables can affect the creation and resolution of a bruise. They then progress to blue, then to brown, yellow, or green.These include type of tissue injured (loose tissue bruises earlier), mechanism of injury, length, duration of force, depth of injury (superficial bruises appear earlier), skin color, health status of the patient, medications (anticoagulants, antiplatelet agents, steroids), and age. Color may help determine “early” or “late” bruising, but more precise timing on color alone is simply not accurate.