by Naa-Dei Nikoi

Spectra is the satellite of one of a system of binary red stars, which means that one of them has to be at least of spectral class K (only class of red stars big enough to support life like we know it) and the other an M class or smaller. Red giants are out of the question. At least one moon, which may have an atmosphere of sorts.
Climate-wise, average planetary conditions seem to be somewhat drier and cooler than Earth, though there are seas, swamps, deserts [ep 99] and polar regions. There don't seem to be forests of any sort -- predominant plant life appears to be grasslike in nature (and we know well of the man-eating plants [39] -- whose adaptability and hardiness gives some clue to how tough life can be there).

I'll have to count more exactly but definite visits were made to Spectra in eps 21, 32, 99, 101. Not a popular destination. :)

While there are (I think) five main categories of stars, so called 'Main-sequence' stars (that make up the majority of stars) are further classified according to their luminosity. There's a good correspondence between the color of a star and its size, brightness, temperature and longevity -- the larger a star, the shorter (more energetic) the wavelength of the light it emits will be, the hotter it will be and the faster it will burn up energy and die. This was first done by Anne Jump Cannon (what a name!) who classified stars from A to I don't quite know if she got to Z. Since her, many classes were consolidated or eliminated and current stellar classes for main sequence stars are O B A F G K M, which I remember as O Brave And Fearless Galactor, Kill My [Roommate Next Saturday] (R, N and S are classes that were dropped not too long ago). Colors refer to the wavelength of the peak emission of that star. O stars are blue (a lot of their emission is ultraviolet), B blue-white, A white (and are brightest because most of their light emitted is in the visible region), F white-yellow, G stars are yellow, K stars are orange-red, M stars are red.
Within each class, stars are further subdivided into 10 categories from 0-9. Our Sun is a type G2 star, btw.

Life as we know it is thought most likely to occur around stars of type F, G and K since they are long-lived enough to support the evolution of life, emit light that is not too energetic (UV, ack!) yet has enough energy to support plant life and have reasonably large habitable zones (the zone around a star in which the surface temperature of a planet will support liquid water). To get back on topic, since canon dictates that Spectra has two red suns, they must necessarily have a type K sun that they orbit since it is the only star class that is both red and can support life. The other star should either be the same size (if it's a close binary system, now I really don't know how the math works out for that) or a lot smaller (if it's not a close binary system -- which works out just fine).

Now note very well that ALL star classes irrespective of color will look white to the human eye and that wherever there is an atmosphere capable of supporting life as we know it, the sky *will* be blue -- Julie found a very nice article on that a while ago. Where red stars will differ most noticeably from yellow stars is that they emit less UV so one will sunburn less readily and plants will need to be more efficient at photosynthesis.

Confused yet? :)

Btw, regarding how often the team went up to Spectra, I missed ep 57 and there's room for speculation come ep 42, when Princess remarks that she's been taping voices of Spectran officers.
And thanks for asking that question -- you just made me realize just why G-Force took so long to start understanding things about Spectra. We the viewers are way ahead of them in that respect.