Why do tall towers and buildings have marker lights on them?  What are
the regulations detailing what kind of ligthts these are?  What is the
required wattage, of these lights?  What is the required color of
these lights?  What is the difference between daytime, night time or
limited visibility requirements?

Hello pringle42 and thank you for your question.

Q. "Why do tall towers and buildings have marker lights on them?"

A. So that aircraft can avoid them "Any temporary or permanent
structure, including all appurtenances, that exceeds an overall height
of 200 feet (61m) above ground level (AGL) or exceeds any obstruction
standard contained in 14 CFR part 77, should normally be marked and/or
lighted."

Q. "What are the regulations detailing what kind of ligthts these are?"

A. The regulations regarding placement, colors to be used etc are
complex because various FPM's (flashes per minute) are required:
"Federal Aviation Administration circular 70/7460-1K" "Obstruction
Marking and Lighting"
http://www.faa.gov/ats/ata/ai/AC70_7460_1K.pdf

(chapter 4 page 9 ((page number is on the bottom right of the page))

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Q. "What is the required wattage, of these lights?"

A. Technical specifications regarding the actual lights are contained in 
"Federal Aviation Administration circular AC 150/5345-43E"
"SPECIFICATION FOR OBSTRUCTION LIGHTING EQUIPMENT"
http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/fd38311187c8a5da86256c690074ffda/$FILE/150-5345-43e.pdf

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Thank you for your question, and if you need any clarification of my
answer, do not hesitate to ask before rating my answer.

Very best regards.

THX1138

Search strategy included:
"red light"  "tall structures"
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