ok i get itNo, these are just the words that the writer has chosen to use. He/She is using "somber" in contrast to "colorful." When the Terracotta Warriors were first created, they were "a supernatural display of bold colors:red and green, purple and yellow." Because they have been buried so long, their colors have been lost and now they are gray, colorless, somber (in color).
And here's procession:
1. the act of proceeding in a regular formation
2. a group of people or things moving forwards in an orderly, regular, or ceremonial manner
So you could have a colorful/loud/joyous/regal procession ... or any of a number of other adjectives.