Fix #3978: Removed unused colors from colors.xml

[ayush0402]

Explanation

Fixes #3978
Removed unused colors from colors.xml.
Followed approach according to https://stackoverflow.com/a/31669368/14822653

Essential Checklist

• The PR title and explanation each start with "Fix #bugnum: " (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".)
• Any changes to scripts/assets files have their rationale included in the PR explanation.
• The PR follows the style guide.
• The PR does not contain any unnecessary code changes from Android Studio (reference).
• The PR is made from a branch that's not called "develop" and is up-to-date with "develop".
• The PR is assigned to the appropriate reviewers (reference).

For UI-specific PRs only

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• Add screenshots for portrait/landscape for both a tablet & phone of the before & after UI changes
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[rt4914]

@ayush0402 Rerunning the test cases as they are failing. If these pass, I can approve it and it should be good to merge. Thanks.

[rt4914]

Tried running it again as I am unable to figure why the test is failing.

[rt4914]

Approving as finally all test passed. Thanks @ayush0402