So, I'd like to paint it to match. Do I need to sand off all the old red paint?
This depends on alot of things, but I won't go into all the various aspects of painting.
Overall, if the paint is not in bad shape (scraped, scratched, rusted) I would advise you to sand (scuff) all the paint EVERYWHERE you are applying paint. After you do this, take a rag and wipe all the dust off. You can use a damp (not wet) rag to do this. Then you can paint it.
For deeper scratches and scrapes, remove the loose material first. Then do what is called feathering out the area. This is simply sanding the area that is now bare (or primer only) and the area immediately around it. You will know when you are done sanding if you move your hand from the paint to the center and across the bare area, then back up to the paint on the other side and it feels smooth. Once again, when done wipe the area to remove the dust from sanding.
If it is rusted, even slightly, take that are down to bare metal. Sand the area out. Prime it with a good metal primer, lightly scuff, then paint.
There are 1001 and one types of ways to remove paint. The cheapest method is your hand and some sandpaper. When sanding the paint, progressively go through the grits from low to high. This is not an auto finish, so if you go with grits higher than probably 240 or 400 (depending on how smooth and shiny you want it), your wasting your time.
The key here is not to make an automotive finish that you can see your reflection in, but rather to ensure that you have a well prepared surface that will let the next layer of paint adhere to it. The last thing you want to do is paint it, let it dry, use it, then next year repaint it.
I have painted steel superstructure, houses, apartments, woodworking projects, concrete, decks, and asphalt, and the same basic premise applies - your finished product will only be as good as the prep work that went into it.
As far as what type of paint to use, make it easy on yourself and just get the kioti stuff. It may not be the market best paint, but you won't have to worry about colors matching or buying the wrong type of paint.
Good luck, and don't forget to tape off or grease the areas that you don't want the paint adhering to (pins, pin holes, scarifiers, or the 3pt moveable areas).
I have to repaint my RFM this spring, and I am not looking forward to that one.
Oh yeah, one last thing, if you have the area, paint the thing indoors. tarp well around the area, and consider using a mask. Almost every painter I have worked with over the years suffers from some "air" issue. Of course some of that is probably due to lunch time at the worksite - puff puff puff.
After reading the post I forgot to tell you that this is probably a bigger job then you think, if you do it properly. I could easily see you spending many hours on this, or spending 30 mintues (paint brush and your hands dripping with paint). The end result will reflect the amount of time spent on the project. Personally, when I repaint my BB, other than removing rust and feathering out the deeper scratches, I could care less if the paint runs or has streaks. Of course you will not likely have people critique your work like I get done to me. I have seen people that expect an automotive paint job on a piece of equipment that will be digging into the ground. Makes no sense to me, but to each his own. Pretty isn't needed, rust free really is needed. Wow am I long winded.