Blue lines in Visual Studio editor margin

Question

I've been seeing these blue lines in the margin when using Visual Studio:

I know the yellow and green lines indicate edits but can't find anything on the blue lines.

Does anyone know what they mean?

Answer 1

Visual Studio uses three colours to track changes; yellow (a change before saving), green (a change after saving) and orange (a reverted change).

See Tools > Options > Fonts and Colors > Track Changes to see these colors.

In dark visual themes, the orange is replaced with blue.

See this question (and this answer) for more details.