Take a gander at: 
http://www.gencourt.state.nh.us/rsa/...-E/270-E-8.htm
for the number display requirements.  These numbers should be as plainly visible as those on your vehicle's license plate.  To not have them properly displayed is an open invitation for scrutiny by the MP that might not otherwise be warranted.  White lettering would be a much better color choice for your red boat.  BTW a hair dryer and patience work well to remove the old numbers and stickers.
  
While we're on the topic, your registration validation stickers come with specific instructions about the location of the sticker, which should be to the 
right of and within six inches ofthe bow numbers, regardless of port or starboard.  That is how they are displayed on my boat.
Sounds picky doesn't it?  Someone in this thread mentioned the 'hundreds of reasons' that could be used to pull someone over for a stop on the landside.    So you have to ask yourself, if someone can't even display their bow numbers in accordance with the law, what other laws or safety requirements might they not be complying with?