Error For input string: "Green" Board configuration Card colors error

[James Tention]

All of a sudden started getting this error on our JIRA Board 

Error

For input string: "Green"

Upon investigation the error only appears when selecting "Priorities" in the Board Configuration–>Card Colors–>Color Based on–> Priorities 

How can I eliminate this error, while still using Priorities as a Card Color.

[James Tention]

Any help on this. The Card colors are unusable when selecting Priorities for Cards. Is it a problem with the installation or a server side admin tweak?

[Jesse Bickel]

More info on the installation (unsure how much is relevant): Version 6.4.2 Database type oracle10g Operating System Linux 2.6.32-504.16.2.el6.x86_64 Clustering OFF JIRA Agile - 6.7.0 (Other plugins: Structure - 2.10.3) Custom Fields 61 Screen Schemes 53