It depends on what you want to accentuate. Color filters merely change how the film sees the colors that are reflected from the scene.

Orange filter makes orange hues lighter, and to a lesser degree yellows and reds.

The complimentary (opposite) color of orange is blue, which means that less of that color will be let through to the film, rendering them darker. To a lesser extent this applies to purple and green.

So, color filters will increase contrast between the color of the filter itself and its complimentary color. But it does not directly alter the contrast of the negative. It just moves tonality around with some colors lighter and others darker than they would appear without the filter.

Film development alters negative contrast directly, regardless of what colors were recorded at exposure. Longer film development = more contrast, less film development = less contrast.
To some extent you can say that film exposure also alters contrast. If you don't give enough exposure some shadow values will be lost, which means that you lose contrast in the shadows, and it also means you have to over-develop which gives more contrast, so it's an indirect effect.

Don't confuse color rendition with overall negative contrast. A green leaf correctly exposed and processed with a green filter will look very light in tone, while one exposed with a red filter will appear almost black.
Look at the link above to see a picture of the color wheel, which further helps explain the reasoning with color filtration.