Copy between layers and retain colors

I have been trying to copy between layers and retain layer colors to prepare files for laser cutting. The only way I can get my laser cutter software to recognize the colors is by reducing all layers down to one one layer when I save the file. If I open a dxf file with multiple layers in my laserCut software it ignores the layer colors.

My process is;

Create layer, edit layer attributes to change color, draw on layer
Repeat for subsequent layers using different colors for each layer
create an 'All' layer.
Select the "All' layer in the layer list
Select all parts in the diagram
Move/Copy
click to specify reference point
click to specify target point
Ensure 'Use Current Layer' is selected in dialog window
->Paste

Sometimes it works, sometimes the target lay reverts to white.

I don't know why.

What I seek to do is effectively merge down all layers into a single layer but retain the color of each layer.

How can I achieve this?

Thank you

If you copy or move entities which have a pen colour property (or attribute) of "By Layer" to a different layer they will get the colour attribute of that layer.

If you want them to keep an individual colour you have to either draw them from the onset with the according pen properties or, select them and change the colour with Tools - Modify - Attributes.