Difference in colour between variable and static builds

[simoncozens]

Prerequisites

• [x] If you are reporting an issue that affects glyphs for characters for a particular region or regions, did you verify that the characters are within the supported scope of the region or regions? This generally means GB 18030 or Tōngyòng Guīfàn Hànzìbiǎo (通用规范汉字表) for China, Big Five or CNS 11643 Planes 1 & 2 for Taiwan, HKSCS-2016 for Hong Kong, the JIS standards for Japan, and KS X 1001 and KS X 1002 for Korea.
• [x] Did you thoroughly search the open and closed issues to avoid reporting a duplicate issue?
• [x] Did you go through the official font readme file to better understand the scope of the project, to include the Known Issues section at the very end?

Description

This is something we noticed when preparing the Noto build of the font for onboarding to Google Fonts. Odd lines are Serif/OTF/Japanese/NotoSerifCJKjp-Regular.otf, even lines are Serif/Variable/OTF/NotoSerifCJKjp-VF.otf at wght=400:

Note especially the strokes of hiragana た、に、で.

I don't know if it's a hinting issue, but this was rendered with Safari on macOS.