I think it must be just my pc that does this.
When I open a new transparent layer and fill it with a color, then it is a transparent colored layer.
When I open a layer with the foreground color red, it is a red opaque layer.... See below, I used red as the color

Double-click your bucket fill tool and see what the opacity setting is. I have a feeling it's not a 100.

it is at 80%..... Just pulled the slider up to 100 and it did the trick and as soon as I went out and back in the slider went back to 80 again. Is there a way to make the 100% as the default?

Thank you very much FP. I thought I was going nuts.....

There's a restore default button at the bottom of the Bucket tool options. When the opacity is at 80%, does it change the opacity to 100%?

If not, again close and reopen GIMP, set the opacity at 100%, Edit > Preferences > Tool Options and click Save Tool Options Now. Then click the Default button and see if the bucket kept the 100% opacity setting.

The reason I said to close and reopen GIMP is so that the tools are set at the initial values and you haven't changed any options before clicking the Save Tool Options Now button.

Thank you "O" I went through all the steps, the first paragraph it didn't stay at 100. I ended up turning it off and going edit > preferences > edit tool options, > turned it off then on and it stayed at 100%....
Thank you, so much.

I have my setting set to remeber the last setting after starting GIMP up again. If I had the gradient tool on difference and close gimp and open it again, all tools with blend mode options are set to difference. Think it's a bug. Wouldn't be surprised if the same thing caused Molly's problem.