Fixed acounts title color propagation

`TransactionsActivity.sLastTitleColor` cannot reliably record the title color of the parent account.
1) It would be changed to -1 whenever `AccountsActivity::OnResume` is called. This would make the variable to be reset whenever an account is to be edited, etc.
2) Account can be changed be selecting an arbitrary account in the whole book. This makes the `sLastTitleColor` not recording the title color of the parent account of the target account.