Are rivers in real life brown, greenish brown, brownish green, or kind of clear, but in pictures they're blue and turqouise, etc.?

Well, of course, the green and blue and turquoise are reflecting the sky.

Brown rivers have drainage from soil. Such as farming upstream.

Clear water will flow eventually anywhere, but particularly of mountain and rocky rivers, usually small ones. Big rivers with boat traffic may look blue because they reflect the sky, but are usually brown or transparent brown.

Green may indicate algae, or plants, but usually the blue-green is a combination of reflected or refracted light and algae.

@Yellowdog How about the difference in pictures and in real life?

Depends where the rivers are. I don’t know why it would be different in a photo than real life, but rivers can be blue or brown just like lakes can be blue or brown.

Picture vs. “real life” can be due to direction of view, time of day, weather, film, filter, camera settings, file format, viewing screen settings, exposure, etc.

Roughly speaking, rivers and lakes mirror the lighting of the sky. The sky may at times be a darker shade in colour than the sky at sunset, twilight, and sunrise.

Water doesn’t look clear or brown or anything in between except when you are close to it, or looking directly into it,

As a general rule, the faster the water moves, the clearer it will be, Rapids would mostly show the white foam and glimpsed reflections or sparkles of sky light / sunlight.

Photographers use filters that produce different effects, some of which can’t be readily recognized, such as a polarizing filter, or even a blue filter.