It is very difficult and unreliable to tell whether a drug has been adulterated by other substances only by color or smell. Many adulterants may not significantly change the appearance or smell of the drug. In addition, the purity and legality of some drugs can only be accurately assessed through professional laboratory testing, so the following points are recommended: 1. **Pay attention to abnormal appearance**: Any abnormal color, spots or uneven appearance may be a sign of adulteration, but it cannot be judged on this basis alone. 2. **Olfaction observation**: Certain chemicals may change the smell of drugs. If the smell is significantly different from the usual smell, this may indicate the presence of adulteration. But many adulterants may be odorless or have a weak smell. 3. **Do not rely on sensory judgment**: Since many adulterants will not show up by color or smell, it is dangerous to judge by these characteristics alone. 4. **Use reagent testing**: There are some reagents on the market that can be used to initially screen the purity and composition of certain drugs, but these tests are not comprehensive. 5. **Consult professionals**: If you suspect that a drug has been adulterated, the safest way is to consult a professional laboratory or medical expert for analysis. To ensure safety and health, the best way to stay away from drugs is to choose drugs that do not use any illegal or unknown ingredients.