Align sign colors for deleting

when the sign deleted, the earlier sign must be coloured.

Look at the sign deletion logic in the Kivy UI code. The issue mentions coloring the 'earlier sign' when one is deleted. Find where signs are displayed and managed, likely in a .kv file or a Python widget class. Check how sign colors are set and what state changes on deletion. A test would involve deleting a sign and verifying the previous sign's color updates.

Written by the indexing model from the issue text.