area/ui: use the same color for similar nodes

[yomete]

This ensures that the same color is used for similar (same node, uuid and index) series in the various utilization metrics graphs.

[alwaysmeticulous]

✅ Meticulous spotted 0 visual differences across 311 screens tested: view results.

Meticulous evaluated ~4 hours of user flows against your PR.

_{Expected differences? Click here. Last updated for commit 387c5c2. This comment will update as new commits are pushed.}