This is why I always suck the old fluid out first.

Then fill the reservoir with either:

1. Blue ATE fluid (which is no longer available).

2. Regular generic DOT4 fluid from local store (such as BrakeBest brand from OReilly). I have used BrakeBest DOT4 fluid for > 10 years in my Volvos, BMWs without any issues.

Is there any detriment to having the blue stain? It sure would have helped me figure out when the transition from old fluid to new fluid was,

Blue is just a colorant.
Similar to washer fluid, Gatorade etc.

Good to hear, thanks for the reply. I think I will try to find the blue kind for next flush, to make sure I do it properly.

Unfortunately, that "blue kind" is no longer available in the good US of A - thanks to our stupid regulations :(

The few unopened containers you do find... are like $100+ for ATE Blue. It's crazy. At the risk of sounding like a conservative (a favorite disclaimer of mine ;)) US regulators think everyone are idiots. Honestly, 99% of people willing to add brake fluid to their cars... already know what and where to add. The last 1% can then take their cars to a local indy and support the local economy some more after they screw up. :D At least then, they will have learned something.