Clairol Nice'N Easy 10 Permanent Hair Dye, 5 Medium Brown Hair Color | 100% Gray Coverage | Natural-Looking Full Coverage Color in 10 Minutes | High Speed & Glossy Finish | Pack of 1

Try something with 100% gray coverage. I just dyed over my blue money pieces and I don't see any of it coming through. I got this one at CVS. I see you are in Germany so maybe you can use this