Photoshop filters

[Geo Flores]

How can I do this effect or filter? any ideas?

[Mylenium]

Layers Palette --> Adjustment Layers --> Gradient Map. You may need to add some Curves or Levels adjustment(s) underneath to adjust contrast and tones.

Mylenium

[Trevor.Dennis]

Also try Filter > Cutout or Posterize adjustment layer to reduce the number of colours.  If you try a Curves adjustment layer as opposed to a gradient map, you need to use radical curve shape like a W.  I think there is some masking in this as the effect would cover those mid tones at the bottom of the image otherwise.