How can the color of valve oil seal be divided into intake and exhaust?

The color of valve oil seal is as follows: 1, dark golden yellow, intake valve green, exhaust valve grayish silver and red. Valve oil seal is a kind of oil seal, which is generally vulcanized by outer frame and fluororubber. The radial opening of the oil seal is equipped with a self-tightening spring or steel wire to seal the engine valve guide rod. 2. Judge whether the valve oil seal leaks oil and measure the cylinder pressure. If it is a piston ring problem, judge the wear amount by the cylinder pressure data. If it is not serious, or it is a cylinder problem, it should be repaired automatically by adding a repairing agent after 1500 km. 3. Check the exhaust port for blue smoke. Blue smoke is a phenomenon of engine oil combustion. It is mainly caused by the wear of piston, piston ring, cylinder liner, valve oil seal and valve guide, but the phenomenon of oil burning caused by exhaust pipe should be ruled out first, that is, the damage of oil-water separator and PVC valve can also cause oil burning; 4. It can be judged by the method of refueling door and releasing throttle that the blue smoke is caused by the excessive wear clearance of piston, piston ring and cylinder liner; The blue smoke from the throttle exhaust pipe is caused by the damage of the valve oil seal and the wear of the valve guide.