One thing most watercolour artists try to avoid is making mud when they mix colours.
Muddy colours appear lifeless or lacking in vibrancy. To avoid making dull colours it's best to use transparent colours when you mix paint.
Opaque pigments, because they are heavier and denser, tend to become dull and lifeless when you mix with them, particularly when you mix two or more opaque pigments together. If you need to mix with an opaque pigment - pair it with a transparent pigment to avoid a thick and heavy mixture.
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