When I started using brushes the other day, it was going great and the brushes were using two choosen colours as the brush strokes (eg. I have the colours set to two shades of green and it using the grass brush it shows blades of grass using a mixture of both colours) wheras now, for some reason it's doing brush strokes in solid colour, the background colour, which isn't what I want. I don't know how to fix this, so I'm hoping someone else has an idea