Unfortunately, there is no standard or internationally recognized colors to specify the level of resistance of loop or resistance bands (such as a range from extra light to XX heavy).
That’s why when you search for Resistance Bands on Amazon.
For example, the WIKDAY resistance bands that I got from Amazon, has the colors as follows..
With yellow as extra light and red as extra heavy resistance. This is not necessarily the standard, and it could be different color progression with other brands, sometimes even the same brand will sell a variety of color combinations.