I want to ask what is water colour pencil in chinese??

It should be "Watercolor Pencils".

1. 水彩鉛筆
2. 文具便有出售 Available in every stationary shop
3. 用水彩鉛筆先著色, 然後在用沾水的毛筆去把水彩顏色勾出來。

The various ways you can use watercolour or water-soluble pencils.

http://painting.about.com/library/weekly/aawatercolourpencilsb.htm

Using watercolour pencils is very similar to using a 'normal' pencil or colour pencil. You hold them the same way, you sharpen the same way, and you can erase them.

It's when you add water to the equation that their uniqueness appears. There are different ways you can do this. For starters, you can do by painting with clean water over your drawing. But you can also lift paint off the pencil with a brush then apply it to your paper, wet the pencil then draw with it, or wet the support you're working on.

Applying a Wet Paint Brush to a Watercolour Pencil Drawing
By 'painting' over watercolour pencil with a brush that's been loaded with clean water, the pencil lines 'dissolve' into watercolour paint. The intensity of the wash produced depends on the amount of pencil that had been applied to paper; the more pencil, the more intense the colour. (It's easier to lay down colour using a blunt pencil rather than a sharp one.) Be selective in which areas you turn into washes to make the most of the unique properties of watercolour pencils (if you turn every bit of watercolour pencil into watercolour wash, you may as well have used watercolour paints to start with).

Lifting Colour Straight Off a Watercolour Pencil With a Brush
To load a brush with a particular colour, treat the pencil tip in the same way you would a pan of watercolour – wet your brush, then use the brush tip to pick up the colour from the watercolour pencil.

Wetting a Watercolour Pencil Before Using It
If you dip the tip of a watercolour pencil into some clean water, or dampen the tip with a wet brush, then draw with it, you'll get lines of intense colour. As the pencil dries out, the line will become lighter.

Using a Watercolour Pencil on a Wet Surface
If you dampen your paper before you apply the watercolour pencil, you'll get softer, broader lines of colour than if you draw on dry paper. Work carefully, and don't use pencils that are extremely sharp, so you don't damage the surface of the paper.

Scraping Colour off a Watercolour Pencil
This is a great way to create texture. Use a knife to scrape off tiny bits of pencil. Sprinkle these onto wet paper, or drop a bit of water on top of them, and watch the colour spread out.

Using Watercolour Pencils 'Dry'
Don't get so seduced by the watercolour properties of watercolour pencils that you ignore the rich colour and detail you get when using them 'dry', in the same way you'd use ordinary coloured pencils. Leave some of the pencil undisturbed, or apply fine detail with a dry pencil once the washes have dried.

水溶性顏色筆
stationary shop
i dont no