From what you have told us, it seems that when you cleaned your knife, a small amount of dishwashing liquid which wasn't rinsed off, dried on your knife, making it look dark-blue.
To ensure a matt and beautiful finish, very small bumps are made on the surface of the blade when it is covered with the titan coating. Because of these tiny bumps, washing liquid can be caught more easily when compared to ordinary knives, if it is not rinsed off carefully. We therefore recommend cleaning and rinsing the knife carefully immediately after use. This type of change in color (due to washing up liquid) can be remedied by cleaning the knife with a melamine sponge. Of course, it is always possible to request a complimentary knife sharpening service.
We don't provide this service as it requires dismantling the knife and removing the old titan coating completely.
Although titan is an extremely hard material which lasts for a long time, it can thin out gradually over time and with the use of a whetstone (notice: titanium is not dangerous if absorbed by the body). We had the opportunity to observe some of our customers' well-used knives where the titan coating has become thinner and we think they had a great atmosphere.
The bolster of Michel Bras knives which binds together the blade and the handle is designed with a curved shape, thick towards the handle and thinner towards the blade ; so forcing the knife into the sheath with excessive pressure may cause cracks in the sheath. Please slide the knife gently back into the sheath to avoid any damage.
Cracks may also occur if the knife drops accidentaly while it is stored in the sheath or if the edge of the sheath knocks against something else.
Have you stored the knife correctly into the sheath? The line on the sheath (located on the side with the serial number) must be aligned to the line on the knife blade (also on the side with the serial number) before sliding the knife into the sheath. The knife may remain stuck inside the sheath if it is inserted in the wrong way.