With symmetric and asymmetric, even at 5, people should always be competing for your cards?
For asymmetric, you will have 2 players going for yellow (2x yellow and 1x financier), 2 players going for blue (3x blue and 1x general), 1 player going for either green/yellow or green/blue.
Going purely green is possible and CAN BE really strong but usually harder than any of the other builds because there's less green cards and in order to produce a lot of green, you'd like very specific cards like Research Centre (which require more white production), Neuroscience for a pure green build is a nearly necessary card for a pure green build, University if you have a yellow/green build and Robot Assistants if you need more white production (which let's face it, we always need more white production).
High point green cards (Time Travel, Teleportation, Unknown Tech) are very few as well, as opposed to the blue and yellow cards. There's also strong multipliers but not necessarily easy to build in a PURE green build (Universal Exposition is a yellow card requiring 3 gold and 2 financiers for 3x science - Parallel Dimension is a blue card requiring 4 exploration, 3 science and a general for 3x science - Unknown Tech is purely green but requires already a lot of green you'd like to put on your other green cards that are producing resources and it also requires a krystallium, thing that is not always easy to get).
In symmetric games, it's more going to be 2-3 players going yellow and blue with hints of green here and there (unless they have the perfect cards to produce lots of green like mentioned above).
At least, at 4p, you'll have pairs of 2 players contesting each other's cards (2 blue/2 yellow) which seems fairer. Keep in mind I don't ever play with asymmetric empires so my opinion might be skewed a bit. I suppose if you have the Panafrican empire (2x science) in variable setup in a 4p game, it's still possible to go green and something else like yellow if there's only 1 other player going yellow (and the other 2 are going blue) or vice versa.
The least balanced setup is 3p though as 2 players will go one way and 1 player will go the other way which means they will most likely snowball very easily compared to the other two contesting each other.
