I see both terms with regards to brake maintenance. Is there a difference between the two or are the terms inter-changeable?
An if they are different, what's the difference?  :dunno:

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Not positive, but I'm pretty sure flushing entails replacing all of the brake fluid in one line/cylinder.
Bleeding is  just getting the air build up out and filling ths remainder of the system.
I may be wrong, but I that's my understanding. :dunno:

Nope, that's the difference.  You can bleed without flushing, but you should always flush by bleeding to keep air out of the lines.

Bleeding removes some fluid, and air in the lines. Flushing is complete fluid replacement.

So flushing is simply the continuous process of bleeding the brake lines while topping up the reservoir until clean fluid starts coming out at the calipers?

With today's fluids, is it necessary to flush every year?
Can the quality of the fluid be judged by its colour?

Yes, I think so, sometimes.  Brake fluid is hygroscopic by nature, and its high boiling point is dropped when it takes up moisture.  I flush my cars every year, and plan to do the same with the bike, just because I never want to be in a situation where I need the brakes and they're not there.

When I flush, I remove the old fluid from the reservior with a syringe first, to make it quicker.  On cars, I alternate ATE Superblue with ATE Typ 200 - basically the same fluid, only one's blue and one's golden, which makes the flush easily seen.  If there's a similar trick with bikes, I'm all ears.

I suck out all the fluid with the vacuum pump and then fill, and I use Dot 5.
Cool.
Srinath.

Quote from: chisterSo flushing is simply the continuous process of bleeding the brake lines while topping up the reservoir until clean fluid starts coming out at the calipers?

That's how I do it.

Quote from: chisterWith today's fluids, is it necessary to flush every year?
Can the quality of the fluid be judged by its colour?

The manuals say to replace the fluid every 2 years.  (See?)  That's about what my experience has shown, too.  My DOT 4 fluid is just now starting to darken up from its original super-pale, almost colorless yellow.  I live in a pretty dry climate ... in more humid areas you may notice the change in color sooner.