magento2 – How to add a default value for the configurable product attribute

My configurable product has 2 attributes (size, color).
When the customer visits the product detail page, I want to set the default value (first value) for the size and color.

Example:
Product1: Size (X, M, L), Color (RED, BLUE, WHITE).

Customer Access to Product Detail Page -> Size M and Color RED are selected.