How strange. What happens if you refresh the texture page? (press f5 on the keyboard). You may lose some progress on the texture you're working on, but that may fix the color issue. If not, can you try using a firefox browser?
Also, it may be that there's a lot of data on your learntomod account, which is causing it to slow down. Or if it's only happening when your sister is using your learntomod account, that may be part of it, because LearnToMod accounts aren't designed to be shared.