The color of the line is insignificant. Pregnancy tests can only tell you if you are pregnant. The darkness of the line is no indication of how pregnant you are or how far along you are. You can use the brand tests, even from the same box and get a lighter or darker line any time.
The phantom calls that you have recieved, also known as ghost calls is usually caused by either a poor quality phone line, aka has a high amount of noise or foreign battery due to the line or your on an older copper line.
Usually in classic horror movies, there's some sort of memorable phone call. Whether it's just dirty talking prank callers, or something supernatural limiting your time to live. The phone has also been used as a weapon, and has had some strange things pop out of it as a surprise for whoever's on the other end.