This section is from the "The elements of drawing & the elements of perspective" book, by J. M. Dent & Sons. Also see Amazon: The Elements Of Drawing & The Elements Of Perspective.
My dear Reader, - If you have been obedient, and have hitherto done all that I have told you, I trust it has not been without much subdued remonstrance, and some serious vexation. For I should be sorry if, when you were led by the course of your study to observe closely such thing's as are beautiful in colour, you had not longed to paint them, and felt considerable difficulty in complying with your restriction to the use of black, or blue, or grey. You ought to love colour, and to think nothing quite beautiful or perfect without it; and if you really do love it, for its own sake, and are not merely desirous to colour because you think painting a finer thing than drawing, there is some chance you may colour well. Nevertheless, you need not hope ever to produce anything more than pleasant helps to memory, or useful and suggestive sketches in colour, unless you mean to be wholly an artist. You may, in the time which other vocations leave at your disposal, produce finished, beautiful, and masterly drawings in light and shade. But to colour well, requires your life. It cannot be done cheaper. The difficulty of doing right is increased - not twofold nor threefold, but a thousand fold, and more - bv the addition of colour to your work.
For the chances are more than a thousand to one against your being right both in form and colour with a given touch: it is difficult enough to be right in form, if you attend to that only; but when you have to attend, at the same moment, to a much more subtle thing than the form, the difficulty is strangely increased, - and multiplied almost to infinity by this great fact, that, while form is absolute, so that you can say at the moment you draw any line that it is either right or wrong-, colour is wholly relative. Every hue throughout your work is altered by every touch that you add in other places; so that what was warm a minute ago, becomes cold when you have put a hotter colour in another place, and what was in harmony when you left it, becomes discordant as you set other colours beside it; so that every touch must be laid, not with a view to its effect at the time, but with a view to its effect in futurity, the result upon it of all that is afterwards to be done being previously considered. You may easily understand that, this being so, nothing but the devotion of life, and great genius besides, can make a colourist.
But though you cannot produce finished coloured drawings of any value, you may give yourself much pleasure, and be of great use to other people, by occasionally sketching with a view to colour only; and preserving distinct statements of certain colour facts - as that the harvest-moon at rising was of such and such a red, and surrounded by clouds of such and such a rosy grey; that the mountains at evening were in truth so deep in purple; and the waves by the boat's side were indeed of that incredible green. This only, observe, if you have an eye for colour; but you may presume that you have this, if you enjoy colour.
And, though of course you should always give as much form to your subject as your attention to its colour will admit of, remember that the whole value of what you are about depends, in a coloured sketch, on the colour merely. If the colour is wrong, everything is wrong: just as, if you are singing, and sing false notes, it does not matter how true the words are. If you sing at all, you must sing sweetly; and if you colour at all, you must colour rightly. Give up all the form, rather than the slightest part of the colour: just as, if you felt yourself in danger of a false note, you would give up the word, and sing a meaningless sound, if you felt that so you could save the note. Never mind though your houses are all tumbling down, - though your clouds are mere blots, and your trees mere knobs, and your sun and moon like crooked sixpences, - so only that trees, clouds, houses, and sun or moon, are of the right colours. Of course, the discipline you have gone through will enable you to hint something of form, even in the fastest sweep of the brush; but do not let the thought of form hamper you in the least, when you begin to make coloured memoranda. If you want the form of the subject, draw it in black and white.
If you want its colour, take its colour, and be sure you have it, and not a spurious, treacherous, half-measured piece of mutual concession, with the colours all wrong, and the forms still anything but right It is best to get into the habit of considering the coloured work merely as supplementary to your other studies; making your careful drawings of the subject first, and then a coloured memorandum separately, as shapeless as you like, but faithful in hue, and entirely minding its own business. This principle, however, bears chiefly on large and distant subjects; in foregrounds and near studies, the colour cannot be had without a good deal of definition of form. For if you do not map the mosses on the stones accurately, you will not have the right quantity of colour in each bit of moss pattern, and then none of the colours will look right; but it always simplifies the work much if you are clear as to your point of aim, and satisfied, when necessary, to fail of all but that. Now, of course, if I were to enter into detail respecting colouring, which is the beginning and end of a painter's craft, I should need to make this a work in three volumes instead of three letters, and to illustrate it in the costliest way. I only hope, at present, to set you pleasantly and profitably to work, leaving you, within the tethering of certain leading-strings, to gather what advantages you can from the works of art of which every year brings a greater number within your reach; - and from the instruction which, every year, our rising artists will be more ready to give kindly, and better able to give wisely.