Refactor color loading and type annotations in color classes

[smnandre]

QA improvements and refactors across the color palette classes,

• stricter type annotations,
• safer data loading, and more robust handling of method arguments

Additionally, development dependencies have been updated for better compatibility and maintenance.

• Type safety and data loading improvements:
• Robustness in dynamic method handling:
• Count method improvements:

Dependency updates:

• Updated development dependencies in composer.json, bumping phpunit/phpunit to ^12.5 and symfony/var-dumper to ^8.0 for improved testing and debugging support.