Conversation so far:
What is an auxiliary in the context of marching bands?
The color guard, or auxiliary, of a marching band or drum and bugle corps may contain sabers, mock rifles, and tall flags.
What did auxiliaries do for marching bands?
Many bands have auxiliaries that add a visual component to the performance.
What did the visual component of auxiliaries do for marching bands?
For ceremonial bands, this could be a traditional color guard or honor guard.
What did being a visual component of bands do for color guard or honor guard?
Auxiliaries may perform as independent groups.
What year did auxiliaries start performing as independent groups?
In the early 1970s, color guards began to hold their own competitions in the winter.
What do color guards holding their own competitions in winter lead to?
Many auxiliary groups change the outfits they use from season to season based on the needs of the band.

Question: What do they change?
Self-contained rewrite: What do auxiliary groups change in their outfits from season to season?