When you are using watercolours, it can be hard sometimes to get a really really good vibrant red.
But I think I have found one.
I did a bit of Daniel Smith shopping recently, and one of the colours that I selected was Permanent Red. This particular colour apparently contains the pigments Naphthol Red and Rouge Naphthol. It is perfect for capturing the intense red of the famous rhodochrosite crystals from the Sweet Home Mine in Colorado.
This particular piece is on a 150x105mm (post)card from Milini. It is 300gsm, hot pressed acid free cotton. Painted using Daniel Smith watercolours and ink.