Hi Sharif, the construction line color can be set in moi.ini - to open that up go to Options > General and there is an "Edit .ini file" button near the bottom.

Construction lines actually use the same color as the lines drawn when "Straight snap" is active, so the value you need to change is the StraightSnapLineColor, which is under the [Drawing Aids] section:

[Drawing Aids]
StraightSnapLineColor=103,0,0,0

The 4 numbers there can range between 0 to 255.

The first number is an opacity value, and then red, green, blue.

So for example to make construction lines white with the same kind of opacity they currently have, set it to this:

StraightSnapLineColor=103,255,255,255

- Michael