I've only just found this thread and joined it very late but I just wanted to answer one question asked very early on by snarkism and show why oceans of even Earth-like planets don not have to (and probably shouldn't all be blue - even for human colonial ones!)
2) Sea colour. You could probably vary the sea colour more from planet to planet - lighter or darker blue (Cyan to Black) - not every planet will have seas of pure water.
Water (i.e. H20) isn't blue - its a colourless liquid (mostly) that looks blue both from space and on the ground due to atmsopheric absorbtion/scattering/diffraction (on Earth) of all shorter wavelengths of light (the blues) - this is why at sunrise and sunset the sun looks very red/orange as as the path length through the atmosphere means some of the greens are diffracted out too leaving only the long wave reds.
What I'm trying to get at specifically is that liquid oceans even watery ones do not have to blue - it is dependant on the dominant wavelength output of the system's sun (is it reddish? if yes - then there wont be much blue to scatter out so the oceans could look green) - is the atmosphere like ours? If human colonials then yes, but not necessarily for others - low amounts of aerosols in the atmosphere (dust/water vapour) and not too much blue would be diffracted out from a yellow/white sun and the oceans could look quite purple in colour.
So that's the physics lesson over and what I'm trying to say is the Earth/Sun combo is pretty unique a slight deviation either side of star peak wavelength output and/or atmospheric content (for small planets that's literal - since they'd have "thin" atmosphere's and almost no scattering of any description even in day light the oceans could look almost black (the planet's sun subtends only a few seconds or minutes of arc - so the majority of reflection would be the blackness of space) makes a huge difference to the "colour" of water based oceans...
Apparently I was having a DaddyHoggy moment.
Oolite Life is now revealed here