Use three colors--black+White+Red

Start with Black
At layer #12 (1.04mm) swap to Red
At layer #15 (1.2mm) swap to White for the rest.

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The X1C framework is linked below

https://makerworld.com/zh/models/87631#profileId-93777

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If you reduce one layer in red, the background will be brighter

At layer #14 swap to White for the rest.