Replace green tones with grey

[sunkup]

Purpose

Staying true to the original design, this PR replaces the M3 green pastel tones used in different UI elements with a grey hue (surfaceVariant) and its dark mode counterpart.

Short description

Replaces the green pastel tones of:

• drop down menus
• collection cards (account screen)
• navigation drawer background and item (selected/unselected)

Checklist

• [X] The PR has a proper title, description and label.
• [X] I have self-reviewed the PR.
• [X] I have added documentation to complex functions and functions that can be used by other modules.
• [X] I have added reasonable tests or consciously decided to not add tests.