Here's what I do know. Many boutique, American amps are capable of running on 230V supply; they need to be configured to do so. Obviously, your friend's Colonial is and is so labeled. The transformer in the Colonial is so revolutionary that Mr. Cochrane received a US patent. Instead of running two different preamps and calling them "Marshall" and "Fender" he used different taps from the transformer to mimic the differences between Fender and Marshall transformers. His design is the only one to do this and does the very best job of producing both brands in one amplifier.
You have a few options:
Either procure a step-down transformer because you know your amp was configured for US standard voltage.
Put your amp next to your friends and see if you can identify the different leads. Be careful, there may be caps and resisters elsewhere that are specific to the EU voltage.
My Favorite: Find a competent repair shop and have them test the leads to see if your transformer is capable of running on 230V. Bring Mr. Cochrane's phone number and have the tech call if necessary.