The best way to assess the color of an object is to compare it against a color standard. One of the most widely used color standards is the Munsell Color System. It is an internationally recognized system that provides an objective method for classifying and measuring color. It uses a three-dimensional color model to classify colors by hue, value, and chroma. It also provides guidelines for how to accurately measure and communicate colors.

If you are looking for a way to convert an object's color from its spectrum to RGB, you can use a spectrophotometer to measure the color of an object and then use a color-matching software to calculate its approximate RGB value. There are a number of different color-matching software programs available, each with their own algorithms for converting from spectra to RGB.