Class java.awt.Color defines a number of constants (Color.black, Color.red,...).
Neither type, nor value for these constants is specified.

Some implementations are known to be using objects of types other than java.awt.Color
to initialize these constants (e.g. on MHP platform type org.dvb.DVBColor is used).

This is causing serialized form incompatibility across implementations:
objects serialized on certain implementations fail to deserialize on J2SE.
This is also the cause of a JCK test failure (api/java_awt/serialization/descriptions.html#Color) on these implementations.
See bugs 4709336 and 6340463 for more info.

J2SE spec should specify concrete types as well as values for these constants.