LÖVE

hi guys,
I would like to know 3 things :
how could i make color spread on the image of the world map without coloring the sea?
how could I create bridge between the country?
how could i create a function that would be trigged later and would also spread color (like the first one
but it would even color the first one)

These are non-trivial questions, we'll need more input. What kind of code have you already built, what kind of game are you making?

Do you want some sort of tile-map where controlled tiles slowly spread out to other, adjacent tiles? Or are you talking more like the fill-tool from a paint-program with high-level accuracy?

(Also this topic should be in "Support", not demos.)

so heres with i have by now :

the game i am trying to create would be a kind of simulator were the color would represent a plague (or a vaccination campaing)
i would like to fill up the blue country with red (the color would spread at a knew speed) and after a few seconds the green color would start spreading at many place in the same time.

I've posted how I would approach the first question, but looking at your larger project, I don't think it's the solution you're looking for. If you want to color each country separately, then I think each country is going to have to be a separate image (solid country, with transparent background), and you'll just change the color at which it's drawn.

But maybe not. Tell us more about the project, or the simulation this is supposed to represent.