Illegal set? I can't move now!

[VOR]

I have a problem and wanted to see if someone could tell me whether or not it's something I can fix...

In one of my games, I have five bonus cards, none of which I actually own. It's asking that I select three to trade in. Whatever I select, it's telling me that it's an illegal set. Well, there is nothing else I can do here. It won't let me select any and it won't let me move on so I'm stuck.

I'm a newbie so maybe this is common knowledge, but can someone give me some direction here?

Thanks!

[boberz]

u dont hv to own them just pick either 3 gren cards 3 rd cards 3 blue cards or one card from each colour.

[kishih]

select 3 of the same color, or 3 cards all of a different color

don't select more or less than 3 cards

[SirSebstar]

What's a set of bonus cards? You earn a card at the end of every turn in which you successfully conquer a country. These cards each represent a country on the map and can be blue, green or red. If you acquire 3 cards of any one colour, or one of each, you now have a "set" of cards which you may exchange for additional armies at this time. The value of these cards depends on which Bonus Cards game option was chosen: escalating or flat-rate. You also get a 2 army bonus on any country that you own if it is represented in the set.

from instructions:how to play