What color(s) of light does a transparent red object transmit? What color(s) does it absorb? What color(s) does it reflect?
Red is the only color reflected and transmitted. All others are absorbed.
Whether an object appears transparent or not, any 'color' we see is the result of the corresponding wavelength reaching our eyes.
“White” light is the impact of all of the available visible light wavelengths reaching our eyes. “Filtering” involves putting materials that preferentially adsorb a wavelength, removing it from those that reach our eyes (or other sensor).
Thus, a “red” object is absorbing all other wavelengths, and reflecting or allowing to pass through only the red wavelength. Whether it 'reflects' or 'adsorbs' is just a matter of the perspective of the viewer – whether the light source is in front of it, or behind it.