求翻译：素描写生练习，注意色彩明度不同的明暗变化，对色彩课的色彩学习也具有实际意义。看不出物体的明暗变化，也就不容易掌握色彩的层次变化，所以说素描也是色彩课的基础。是什么意思？

Sketch practice, pay attention to changes in light and dark colors of different brightness, the color of the color class learning also has practical significance. See changes in light and dark objects, and not easy to grasp the level of color change, so that drawing is the basis of the color class.

Sketching sketching exercises, noting the colors different shade of color, change the color lesson learning also have practical significance. Do not think that the shade change objects, it's not easy to master color levels, therefore it is said that changes color sketching is also the base class.

The sketch sketch practice, the attention color brilliance different light and shade change, also has the practical significance to the color class color study.Cannot see the object the light and shade change, also not easy to grasp the color the level change, therefore said the sketch also is the c

Sketch practice note color Brightness in different light and change color study on lessons of color also has practical implications. Cannot see objects of value changes, it's not easy to master the color of the layer changes, so this sketch is also color of Foundation.

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