R1:95df7717c3e8

Ref T6500, Duplicated tasks should be marked more visibly as duplicates

Summary: When merging tasks, the corresponding transaction on the merged task should be black, and the transaction on the ultimate task should be green.

Test Plan: Create two tasks, merge one into the other, merged task transaction is black, the surviving task should show a green transaction.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: chad, Korvin, epriestley

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