Red & Blue anderson plug

You need to know exactly what they are for. As you said the different colours do not mate. The grey one is usually used for 12v power. If you connect the wrong circuits together you may end up with embarrassing smoke. They must be different colours for a reason. For instance I use grey for 12v and yellow for my solar panels unregulated power.
If you determine they are 12v you don't need an adapter, you can change the outer shell to grey.

'new' as in new to you or brand new?
brand new, take it to the dealer.
2nd hand, first put a multimeter on them to establish if they are live and which is +ve or -ve.
probably need to find out where the cable goes and if it's fused etc.
no adapter needed, re-terminate the cables onto an anderson plug if required.

First step would have to be to trace the cables back to see where they go and what they're used for. Are they 12v ?
From there you can decide the next step.

They look to be the Anderson PowerPole fitting.
http://andersonconnect.com.au/store/index.php?main_page=index&cPath=36_41

Alright, confirmed its a 12v running to the 2nd battery.

We used to use the blue and the red plugs in Telstra solar installations at towers and radio sites. Reckon 20 amps max. The grey are 50 amp.

Certainly not the accepted grey Anderson plug that everyone uses.

Cut them off and buy a grey one and either crimp or solder the cables in

These are Anderson plugs called Power Pole connectors. They are rated at 30 amps so should be sufficient for most applications such as fridges or low power inverters. Jaycar sell then so if you want to use the existing cable get the mating connectors there for what you want to power. I'd use them rather than cut them off and replace with the single Anderson plug.
Ken

I have read that the red Anderson sockets are often used to provide a dedicated 12V to the Al-ko ESC system.
Perhaps that it what is was for!

Ken

Here's a bit of info about them.
http://www.jaycar.com.au/Interconnect/Plugs%2C-Sockets-%26-Adaptors/DC-Power/30A-Anderson-Powerpole-Connector-Set/p/PT4405

Cheers, Bob

Comms related? Perhaps they supply 30 Amps to an HF radio.

Bob

Those power pole plugs have been around for a long time - I used them with DC stuff about 25 years ago. They were versatile because they are single plugs, both sides are shielded, they interlock so you can make up a series of 1,2,3,4 or whatever, and when you interlock them, you create a screw hole so they can be surface mounted.

But they were a bit bulky and got replaced by many other connectors that could carry more current and were twin. The common grey anderson plug has become so widely available and incredibly cheap that it is what you see most people using for many RV applications, and I'd also give the power pole the chop and just use whatever suits your needs.

There are lots of references to grey Anderson plugs on this forum.

I am not sure why but lots of people think they are 50A. maybe the 50 in the product number.

The Grey Anderson plugs are rated at 120A.

These are Anderson Power Pole connectors. Most likely the PP15-45 size. These are different to the Anderson "SB 50 series" connectors that we know as the grey 50 Amp connectors and do not mate with each other. Anderson make a large range of connectors. These two are the most commonl styles seen in the camping world in Australia

The Power Pole connectors come in 4 different sizes and several colours. The PP15-45 is the smallest. There are different size pins/contacts available to take different gauge wire for each size connector. In all cases, the actual contact dimension is the same for the pins that match the connector, just the hole size to accept different gauge wire varies.
As these are designed to be crimped, the different size pins give best crimping to different size wires. These connectors are rated up to 45 amps.

The same concepts are also applied to the SB series connectors. There are also 4 sizes and come in different colours. The ones we know of are the smallest size housing in the series (other sizes go up to 600 amps!) Unlike the Power Pole connectors, there are supple mechanical difference in the SB series (even though they look identical) that prevent the different colours mating with each other. Like the Power Pole connectors they also have different pins to take different gauge wire.

The Americans being Americans seem to have adopted the practice of calling the different size contacts by the current the wire intended for that pin is able to carry.
Hence the 50 amp connector is a standard SB50 housing with a contact with the largest hole size contact available, but contacts with smaller holes to reliably crimp smaller gauge wire are available.
We would most likely call the contacts 13mm, 6mm or 5.3mm contacts.
This size housing is rated up to 120 amps with appropriate contacts.

As to the OP, I would suggest tracing back the wires to see where they are sourced from and making a decision as to what to do from there. They may be 2 x 12v sources, each fused differently, or one switched by the ignition, one permanent power or maybe the blue is actually an earth because the installer had no black wire(???). Only tracing will tell.
The OP can then decide to buy Power Pole connectors to use the existing, or re-terminate in a connector of his choice.

I use the Power Pole connectors a lot due to their small size. They can carry all the current I need for everything around my camper and car without the bulk of the SB connectors. Where a physically more rugged connection is required (ie on the bumper supplying battery power to the trailer ), the SB50 is used.

Goggle "Anderson Power Products" for info and purchase sources.