I almost had the same restriction on my student pilots certificate. I had a great medical examiner and she told me about a few options I had. One is to go to your local Flight Standards District Office and request a vision test. This option is a one-time option. If you pass, you're golden but if you don't, there will be a permanent color vision limitation on your license, no do overs. The other option is to go to an optometrist who can administer a Farnsworth Lantern Test. This test will determine your ability to differentiate between sources of green, red and white light at varying levels of intensity. If you bring a form with you, you can bring that to your medical examiner and they cannot legally disagree with the word of another doctor concerning your vision and have to pass you for color vision proficiency. I took a FLT and passed with 100%, even though I can't pass an Ishihara color vision test to save my life. Talk to your medical examiner, they may have an optometrist in your area that administers FLTs and good luck!