No. However, that’s the best strategy if you like what you see. The names of watercolor paints only vaguely define a color. Cadmium red varies from manufacturer to manufacturer because they use different pigments and different formulas to make that color. In other words, a cadmium red from one company might be a darker shade than a cadmium red from another. If you know and understand this, you can use it to your advantage. If you’re unaware, you could ruin a painting by applying a color that you think is the same. For consistency, it’s best to stay with the same manufacturer, but for creativity’s sake, you can certainly mix and match.