Create closed areas from open areas

Question

I should convert mono-colored seamless pattern to colored one. The problem is -instead of masking, the shapes were cut at the perimeter and expanded, thus using live paint is impossible.

I look for a simple way to "re"-create an area enclosed by cut edges, i.e. connect 2 points to "close" the area and to color it.

For example, I have this cut shape -

Which is expanded, so there is no "area" to fill -

I need to fill the cut open areas with colors - the apexes are pointing to the areas to fill. Grey color is Ai background.

How can achieve that with minimal efforts instead of recreating and masking the whole pattern?

UPD if it unclear, I moved the object to the right to show that the areas of interest are open spaces, not enclosed areas or objects bounds -

Answer 1

Use the Live Paint Bucket Tool.

• Select the art
• Grab the Live Paint Bucket Tool
• Click once to create the Live Paint Group
• Pick a color
• Click the areas to fill them with color

To get back to standard objects, simply click the Expand button on the Control Bar

Edit:

I missed that the left side was the artboard, not a grey object.

For hollow objects, just draw a rectangle on the left side.... use the Live Paint Bucket... expand.. delete the rectangle.

You could also draw a rectangle behind the shapes and use Pathfinder > Trim. Then delete any unwanted pieces.