You don't use vector databases independently, you need to input the embedding from a ML model.

For your use-case, it should be pretty simple. You could use a CNN and train it, or use YOLO, Deepface, or other face detection algos, then within the face, find the hair and find the skin.

From there you can use a vector database to get the colors that resemble other inputs, or you can use a simple CNN to classify the hair and skin to the closest label.