Due to the low degree of mineralization, deciduous teeth are chalky.
The degree of mineralization of permanent teeth is very high, and the outermost enamel is almost transparent, which can expose the yellow dentin inside, so it looks yellow under normal circumstances.
At this time, there are both white deciduous teeth and yellow permanent teeth in the mouth, and the contrast between them makes the permanent teeth yellow.
If you still feel yellow after all your teeth have been changed, you can do cold light whitening after 18 years old.
Before that, health is the most important thing.