Fix wrong color of contract icon on xDai chain

[vbaranov]

Motivation

1. Wrong color of contract icon on xDai chain

2. Merge to master currently deployed to blockscout.com theme for xDai

Changelog

Checklist for your Pull Request (PR)

• I added an entry to CHANGELOG.md with this PR
• If I added new functionality, I added tests covering it.
• If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.
• I checked whether I should update the docs and did so by submitting a PR to https://github.com/blockscout/docs
• If I added/changed/removed ENV var, I submitted a PR to https://github.com/blockscout/docs to update the list of env vars at https://github.com/blockscout/docs/blob/master/for-developers/information-and-settings/env-variables.md and I updated the version to master in the Version column. Changes will be reflected in this table: https://docs.blockscout.com/for-developers/information-and-settings/env-variables.
• If I add new indices into DB, I checked, that they are not redundant with PGHero or other tools

[coveralls]

Pull Request Test Coverage Report for Build 34168d69-8b95-48cf-8673-71474ba8f6e8

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 15 unchanged lines in 6 files lost coverage.
• Overall coverage decreased (-0.2%) to 76.471%

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Files with Coverage Reduction	New Missed Lines	%
apps/explorer/test/support/factory.ex	1	92.97%
apps/indexer/lib/indexer/fetcher/token.ex	1	80.0%
apps/indexer/lib/indexer/fetcher/token_balance.ex	2	87.88%
apps/indexer/lib/indexer/block/catchup/bound_interval_supervisor.ex	3	85.19%
apps/indexer/lib/indexer/block/fetcher.ex	4	86.75%
apps/indexer/lib/indexer/fetcher/token_instance.ex	4	0.0%

Totals
Change from base Build e16f52a5-6f94-481e-89c0-376d479d2e8f:	-0.2%
Covered Lines:	5301
Relevant Lines:	6932

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💛 - Coveralls