The Five Main Ones

Question

Here is a classic A is to B as C is to D puzzle. Try see if you can figure out the answer.

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$F:BRW::I:GRW::P:GR::R:BRY::?:?$

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Note: Some minor simplification was needed on some of them. But that shouldn't cause any problems solving the puzzle. Once you see the pattern, you'll realize what the simplification was.

Answer 1

The answer is:

S : RY

Reasoning:

The left side of an analogy is the first letter of a country which defines a Romance language: France, Italy, Portugal, Romania. The right side of the analogy is the first letters of the colors on its national flag, sorted in alphabetical order.

France: Blue, Red, White
Italy: Green, Red, White
Portugal: Green, Red
Romania: Blue, Red, Yellow

The missing member is Spain, with a red and yellow flag, hence S : RY.

As an additional check, notice that in the presented analogies the countries are also in alphabetical order.