Hello and welcome to HCM,
with different colors in the center and the periphery is a classical example of resolving bruise.
Bruises occur due to blunt trauma
to the skin.
However, you do not memorize being hit by any object or trauma; but it is unlikely to be due to any other cause.
If there is history of frequent bruising, you need to consult your hematologist
for evaluation of platelet function tests and coagulation profile.
If this is an isolated example then you needn't worry.
Thanks and take care
Dr Shailja P Wahal