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.
A busy signal (or busy tone or engaged tone) in telephony is an audible or visual signal to the calling party that indicates failure to complete the requested connection of that particular telephone call. The busy signal has become less common in the past decade due to the prevalence of call waiting and voice mail.