Terraforming colonists -> can't produce on 'deserted alien outpost'

[wimleenaerts]

I get the message 'Produce: You must choose which windfall world produces a good during this phase' because I have Terraforming colonists but when I select my 'Deserted alien outpost' I get the following message: "None of your powers allow you to produce on this world "

Also, there is a blue square with white -4 in the bottom right corner of my 'terraforming colonists'. What does that mean? edit: just found out this is a starter card.

[Nog_eentje_dan]

Terraforming colonists requires you to discard a card from your hand to produce a good. Maybe your hand was empty?

[galehar]

You need to select a card from your hand (to be discarded) before clicking on the windfall world you want to produce on.

[wimleenaerts]

You need to select a card from your hand (to be discarded) before clicking on the windfall world you want to produce on.

Aha, that might be it!
I had enough cards to discard but I didn't get the request to select a card to discard, I supposed I'd get the request once I selected the windfall world. I'll try it next time the phase comes up. Thanks.