I see this is a couple weeks old. I've never made compost tea myself, although I have considered it. The only thing I wanted to mention is that sometimes, if a plant isn't reproduced/bred properly (wherever it was mass-produced), it's blossoms can change to white over a year or 2. I've had that happen with a couple of my plants. Just thought I'd mention that as a possibility.

There are a number of reasons why a flowering plant might change color, including catherinet's explanation, but you can rest assured compost tea is not one of them :-). All compost tea is is a low grade liquid fertilizer. There is nothing in it that would alter plant pigmentation.

There are a few things you should know.

1. Composted manure is compost. It is no longer manure.

2. Compost tea can only be made using an aerator to keep air in the water. What you made was, at first, compost leachate, where the nutrients, if any in the compost, washed out into the water. It's not a bad thing if you use it right away, but it is not a "tea" in the agricultural sense of teas. If it is actively aerated at temps in the low 70s or below, you have a chance of it being compost tea.

3. Water at a temperature above 75 degrees holds very little oxygen. If you live in a warm climate and your barrel was outside, then the best oxygen content you could achieve is 0.00000% dissolved oxygen even if you bubbled air through it in a torrent. If you live where the high temp was in the mid 70s, the best you might achieve is really low with continual aeration.

4. Aerobic microbes use up oxygen quickly. Since you did not supply additional oxygen, no matter what you had 0.00000% dissolved oxygen after a few hours. This means the only microbes able to survive are the anaerobic microbes. Usually these are associated with disease, but that's probably not entirely the rule. You can find this situation in any pond toward late summer. The shallow parts of a still pond become warm and will develop an algae bloom resulting from oxygen depletion and growth of anaerobic microbes.