[java.lang.NoClassDefFoundError: Could not initialize class java.awt.Color]

Ok, there seems to be a workaround solution for this issue.

First, if you are opening .jrxml file made from older version of Jasper Reports, make sure you go to "Window->Preferences->Jaspersoft Studio->Compatibility".
Then choose appropriate Version for source .jrxml Version and then "Apply and Close".
Now exit Jaspersoft Studio and delete .project file from project directory that you are opening.
Run Jaspersoft Studio, delete project directory from "Project Structure" but don't check the option for deleting files from disk.

Now open project directory and you should successfully open .jrxml file from Jaspersoft Studio.
Process is tedious but it works until you exit Jaspersoft Studio.

[java.lang.NoClassDefFoundError: Could not initialize class java.awt.Color]

I am also having the same problem when trying to open .jrxml file with Jasper Studio 6.19.1.
The same .jrxml file is opening fine from iReport 5.6.0.
Does anyone know how to fix this problem or have some idea for workaround solution?