COLOUR (Part 2)
If you mix too many colours together, you'll get mud. If your gray or brown isn't coming out the way you want it to, it’s best if you start again than add more colour in the hope it'll work.
The complementary colour of a primary colour (red, blue, or yellow) is the colour you get by mixing the other two primary colours. So the complementary colour of red is green, of blue is orange, and of yellow is purple
When placed next to each other, complementary colours make each other appear brighter, more intense. The shadow of an object will also contain its complementary colour, for example the shadow of a green apple will contain some red.
While it may seem logical that to lighten a colour you add white to it and that to darken it you add black, this is an oversimplification. White reduces brightness so although it makes a colour lighter, it removes its vibrancy. Black doesn't so much add darkness as create murkiness (though there are instances in which black is uniquely useful, such as the range of greens it can produce when mixed with yellow!).
Adding white to a colour produces a tint of that colour, makes a transparent colour (such as ultramarine) opaque, and cools the colour. This is most noticeable with red, which changes from a warm red into a cool pink when you use titanium white. You can add white to lighten a colour, but because this removes the vibrancy of a colour you'll end up with a washed-out picture if you use white to lighten all you colours. Rather develop your colour mixing skills to produce hues of varying intensity. For example, to lighten a red, add some yellow instead than white (or try zinc white)
Black tends to dirty colours rather than simply darken them. Of the most common blacks, Mars black is the blackest and is very opaque, ivory black has a brown undertone, and lamp black a blue undertone.
Think about how much is truly black in nature. Shadows are not simply black, nor a darker version of the colour of the object. They contain the complementary colour of the object.
Take, for example, the shadow on a yellow object. If you mix black and yellow, you get an unattractive olive green. Instead of using this for the shadow, use a deep purple. Purple being the complementary colour of yellow, both will look more vibrant.
It's not true to say the Impressionists never ever used black, but they certainly popularized the idea that they never did.
If you can't see yourself working without black, then consider mixing up a raw umber with ultramarine rather than using a straight-from-the-tube black. It also has the advantage of not 'killing' a colour it's mixed with to the same extent.
Opaque pigments are dense and tend to block out other colours. This makes them ideal for subjects that are solid and heavy, such as tree trunks. Transparent pigments are light and airy, barely showing on top of other colours. This makes them ideal for atmospheric subjects such as a misty morning or diaphanous fabrics.
