Wa codes are "different" to say at the least.

Your color code could read  "U 9260"

And what that turns into is WA9260 which is a very common red for all General motors products. 

So we have 3 "WA9260" codes. 

Now every paint company reads that differently.  Akzo will read it with any code with a U, without a U, or WA, and they use the manufacturer (such as chevy, buick or gmc to lookup). And Akzo uses the front number too.  Basf will just use the WA number along with or without the 2-3 digit front number ( 74 or GCN ). Debeer uses the 74-9260 code.  Prospray uses the same as Basf but for newer colors you don't have to use the WA in front.  Concept paints (Transtar No Mix) uses the front digit code and or the WA code without using the WA via lookup (example you can't type in WA9260, you could use the GAN, or 74, and only the 9260 part). 

So if you are still reading this, if you need touch up paint the most important part of this is just go in and give the front digit (74, GCN) or just the Number (9260) or number and a letter part (example look up WA926L,  you could just say 926L) along with the year of the vehicle.  

As far as the 3 different WA9260's go, they are different shades for every code. 

Putting paints on different parts of the car (new paint on bumper doesn't match the new paint on the car is because there are variants for every color.  For instance we are now in a world wide economy and it's cheaper to paint the bumpers in Mexico and cheaper to paint the doors in Italy (all examples and cheaper meaning labor or you have to have a plant in a country in order to sell your product there) and  assemble the main body car that was painted in America.  That's why the bumper never matches the rest of the car.  You have all kinds of factors like humidity, air pressure, paint assembly hoses not completely cleaned out, a scratch that needed redone and so on.   OEM paint for the most part is different than aftermarket paint.  The higher end paints try really hard to accommodate all those conditions when matching paints.  Lesser money brands like Limco are great products but they will make maybe a standard paint formula and maybe a variant. The lesser money brands don't really put money into color matching like the paints that are 5 to 10x more, but the market is changing and now programmers are developing cameras that are really close to "panel painting" colors now without even a paint code.  In my mind Akzo has the best camera, but Basf, and Concept Paints (Transtar No Mix) also have an excellent camera.  I've been using the Akzo Camera for 6 years, and it's worked amazing on everything.  I haven't used the Basf camera for 10 years, but all the painters I know absolutely love it.  I use the Transtar Camera a lot too, and it is actually cheaper than Limco at Medium Solids ready to spray, and it does amazing.  So in conclusion paint codes will become a thing of the past and cameras will be the way to go, because the market of car paints seems to be going to "Bespoke" Oem.