Final answer:
The most valuable tool for identifying natural level in hair coloring is the hair swatch. For pH measurement, pH meters and pH indicator papers are commonly used in laboratories to determine the acidity or basicity of a solution.
Step-by-step explanation:
Your most valuable tool for identifying natural level is the b) Hair swatch. This question is related to hair coloring in the field of cosmetology, not chemistry. However, discussing the measurement of pH, it's commonly done in laboratories using digital pH meters. These devices are calibrated with solutions of known pH values and can provide an accurate reading of the pH of a test solution. Another method for estimating pH is using universal pH indicator papers, which change color according to the pH of the solution they come into contact with. To determine the pH, you match the color of the indicator paper to a color chart. pH strips and meters are tools developed to make the measurement of pH simple and convenient.