Same color, same alpha-based fade distinguishing it from the actual measured trace - just '-b' instead of '--b'. Updates the surrounding docstrings/comments and README that described it as dashed. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01DkkuG48uHFCGKe6dPSERFk