Pink shading on a quality control metric indicates that the metric is higher (or lower) than the threshold defined for Astrolabe. We defined the thresholds based on our experience with a large number of experiments.
Please note that the thresholds should not be taken as an absolute truth, as every experiment is unique and false positives are always possible. Specifically, having a handful of samples with oxidation ratio slightly higher than 0.5 or with an alert on signal stability is standard. However, if you see a trend over multiple samples that belong to the same batch or over the entire experiment you might want to examine them more closely.