I am looking at a FN mauser that looks to have an aluminum trigger guard and floor plate. they are in need of some color... how would one do that? can a guy set up commercially to blue/park etc be able to color aluminum?

the gun looks to be in good condition and for $300 i think a pretty good buy.

There are baking lacquers and spray paints, but the more durable finish would be to have it anodized. Call a plating shop. Some of them specialize in a wide assortment of colors.

Check out US Anodizing Lots of colors and finishes available in house or D-I-Y kits. www.usanodizing.com

Airgun1 hit the nail on the head.
I use to anodize in my garage. It's pretty easy to do just a little time consuming and the process never stops once begun. you have to complete all the steps in one day or don't bother.
Caswell is another good source.

Pulled from my old web site

Anodizing
First off I’m no expert at this. What I know is from pure trial and error and research on the web and talking with people in the industry. I’ll explain it the way I learned and make it as easy to understand as possible.
Lets start off with what Anodizing is as a process and as a surface treatment. Anodizing is a controlled oxidation of the surface of an aluminum part that can be a very hard and very durable surface. Type II anodizing is the process we are talking about here since I have never performed Hard Anodizing (type III) I will only say that it is performed in a cold acid bath at higher current levels to achieve the hard layer. ( because that is about all I know about the process )
Type II Anodizing is a very simple process that is performed in a sulfuric acid bath that is around room temperature plus or minus a few degrees with approximately 65 degrees F being Ideal. As DC current is applied through the part and a plate in the acid bath a reaction happens that causes the surface of the aluminum to change to aluminum oxide. The longer you leave the part in the bath the thicker the layer of aluminum oxide will be, But only to a point because as it gets thicker the acid is also eating away at the newly formed layer and it will reach a point of equilibrium and the layer will cease to grow. The typical thickness is only about .001.

The acid that is used is sulfuric acid and it is in a very dilute concentration. Around 10% acid to water is typical. I start off by buying pre mixed battery acid from Napa auto parts. A 1.5 gallon container is around $8.00 Then mixing this with distilled water at a ratio of 3:1 water to acid makes about 6 gallons. In my experience plus or minus a half gallon is not critical. ALWAYS MIX ACID WITH WATER NEVER WATER WITH ACID. Meaning pour your water into a container suitable to contain acid and then add your acid to this. Doing it the other way will create so much heat that you can cause the water and acid to boil. Very bad. It can get hot enough to melt the plastic container it’s in.

Power supply and set up.
I use a 12v variable current power supply that can handle up to about seven amps. This is about ideal for small parts. A lead or aluminum plate is placed in the bottom of the bath and the negative side of the power supply is connected to it. The part needs to hang in the bath buy a aluminum wire or titanium wire and connect it to the positive side of the power supply. Set your amps based on the part’s size and turn on the juice. Sit back and watch it run for about an hour then rinse in cold clean distilled water. then either dye the part in a heated dye bath (no hotter then 125 degrees F) then seal in a boiling water bath again clean distilled water.
Then polish with simi chrome or duraglit polish and thats it your done. Now I know I left out a lot. But I'm not going to reinvent the wheel here. Caswell Plating has all the info and supplies you could ever want.

What I will tell you is that it is a royal pain to do and you can not stop for very long between steps. As in minutes. If you stop for an hour or longer you run the risk of contaminating your part or allowing an oxide layer to build up. Either way this is bad. The part needs to go from the degreaser to the rinse to the anodize solution to the rinse to the dye to the sealer in one movement. with little to no delay between steps especially after anodize and before dyeing or sealing. This is the critical time to get things done. When I anodize I plan the day around it.
Bath temp is another critical part. If the bath is to hot the anodize layer will be to soft and will not hold up to any use. You must keep the solution temp at or near 65 degrees F and no hotter then 75 degrees F.

Clean distilled water must be used. Reverse osmosis is OK according to Caswell But I have had no luck with it and well you have no clue when the last time the filters where changed. So just go and buy distilled water and use it for your anodize solution, rinse, dye, sealer, and stripper. DO NOT USE TAP WATER. or bottled drinking water. It has minerals in it and will contaminate your parts.
One key is absolute cleanliness. Use of rubber glove is essential and rinsing them along with the part at each step is critical. Use of long cuff Nitrile gloves also recommended for handling parts to and from the acid bath

Stripping parts.
Stripping can be done with Pure lye and distilled water 1 Table spoon per gallon is enough to strip parts clean of the anodize layer. Red devil lye was the stuff to use but it has since been discontinued due to drug manufacturing. But once again Caswell will supply a stripper that works perfect.
I know I’m plugging Caswell But they have been a great help in being able to get supplies and info from. They pay me nothing to post my opinion. I’m just a loyal and satisfied customer.

Here’s the steps in a very basic form
1. Part preparation. The part should be clean and polished ready to go with no anodize layer on it.
While wearing rubber gloves dip the part in heated degreaser and gently wash it with a rag or soft cloth for finely polished parts or a tooth brush for parts that are bead blasted or scotch brite finished
2. Rinse in clean cold water.
3. At this time you can use a product called Desmut this is a chemical etch that further removes oxide layers. Rinse after Desmut dip.
4. Secure part on an aluminum rod (welding rod works well) or use titanium wire to hang part in acid bath.
5. attach negative lead to a plate in the tank and attach positive lead to hanger wire that is outside of the tank.
DO NOT LET LEADS (WIRES) TOUCH BATH, DO NOT LET ANY OTHER METALS COME IN CONTACT WITH ACID.
6. Connect leads to power supply (rectifier) and set amps accordingly. 30 milliamps per square inch of surface area
7. Let part run for approximately 90 minutes.
8. Dye part in heated dye bath (110 Degrees F) until darker then color desired.
9. Seal in boiling water or add sealant powder from Caswell.
10. Lightly polish with a soft cloth and some simichrome.
Sit back and admire your work