To help you when googling for cards and things, the second digit is an L not a 1. It is an RL80C. To answer your Qs:
Age - likely 200 to 2004, ish
Colour - yes (the "C" means colour). Charts will show in full colour. However, the radar function is not digital so although radar targets will show as yellow blobs on a black background, which you could say is "colour", it will be monotone really ie ONLY yellow blobs on black background
Cards still widely available
Have just bought a new card for my RL70(next sized down screen).You can get latest local area chart for about 110.00 delivered.
Wide area charts are more expensive but not vital unless you venture far afield.
Worth searching Ebay for S/H charts if your local knowledge is good and electronic navigation is not to critical.
If your plotter came with seriously outdated cards or from different area they can be upgraded for around 70.00.