Turns out, her matcha wasn't terrible. It was just old. The harvest date on the bag was over a year ago. Once she switched to a fresher batch (within six months of harvest), the color improved dramatically.

Here's a quick checklist you can use before buying:

1. Harvest date: Look for 'harvested' or 'picked' date, not just 'best by'. Within the last 6 months is ideal.
2. Grind date: Matcha is ground from tencha leaves. The finer the grind, the fresher it should be. If it's pre-ground, check when it was ground.
3. Country of origin: Japanese matcha is the gold standard. Chinese matcha can be good, but it's more variable.
4. Color after whisking: Bright green with a slight yellow-green tint is a sign of good quality. If it turns brown quickly, it's likely old or low-grade.

Also, check your water. If your tap water is hard or high in chlorine, it can affect the color. Use filtered water if you can.