Fix: increase color contrast of input fields

[Nishthajain7]

Issue:

Fixes #3944

Demo:

Light Theme

Before





After

Dark Theme

Before





After

Changes:

Increased the contrast of the input fields

Steps to verify

1. Switch to Light theme
2. Click on the > button to the left of file name
3. Click on the + button to create a new file
   Notice the difference in contrast. Repeat the steps in Dark mode as well

I have verified that this pull request:

• has no linting errors (npm run lint)
• has no test errors (npm run test)
• has no typecheck errors (npm run typecheck)
• is from a uniquely-named feature branch and is up to date with the develop branch.
• is descriptively named and links to an issue number, i.e. Fixes #123
• meets the standards outlined in the accessibility guidelines

[yugalkaushik]

LGTM