Colors: Migrate color shades from HSL to OKLCH

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Currently all color shades, bar the 500 variant, are in the HSL color space. Switch to OKLCH to ensure better color representation on most modern displays.

Here are some of the benefits:

• Perceptual Uniformity: Colors in OKLCH are more consistent with human perception, making adjustments (e.g., lightness or saturation) visually predictable.
• Improved Accessibility: Easier to maintain contrast ratios for WCAG compliance, as lightness directly correlates to perceived brightness.
• Wide Gamut Support: It accommodates a broader range of colors, especially in modern displays with extended gamuts.
• Hue Consistency: Changes in chroma or lightness don’t shift the perceived hue, unlike HSL.