[web] Finish styling ColorSelector on iOS and Android

Summary:
Completed styling ColorSelector on iOS and Android using different devices and breakpoints.

Part of ongoing redesign of ColorPicker component. Relevant Linear issue here.

Depends on D3939.

As @atul pointed out in the last diff, any code changes that could break something else shouldn't be committed, but noted in the Summary. This is a change that was made to better encompass the new ColorSelector. The height of the ColorPickerModal was modified to:

Test Plan:
Looks and works as expected on iOS and Android devices. Note the small and large devices (iPhone SE and iPhone 13 Pro Max, for example):

Reviewers: atul

Reviewed By: atul

Subscribers: varun, ashoat, palys-swm, Adrian

Differential Revision: https://phab.comm.dev/D4254