what would you see if you looked at red writing with a red filter? what colors does the filter pass? and what colors would a blue filter pass?
therefore, could there be a way to determine the colors of celestial objects by using red and blue filters?

That would depend on the light which illumines the writing. With white / red light it should appear red but if it is illumined with monochromatic radiation of some other colour it should appear black. The wriring looks red to us because it reflects only the red wavelength and absorbs the others. If we use some other colour light, that would get absorbed and so it wouldappear black. Blue filters transmit blue light.
Spectroscpoes are used to study radiation from stars . In these, the incident light is either dispersed or diffracted and we get a line spectrum. Study of the intensity and wavelength of these lines gives us an idea of the concentration and presence of different elements in these stars