Decide what colors you want to dye. This will determine how much of each color you will need, whether you are using them individually or in combination. If you need a lot of dark green, for example, you'll need to buy more blue than yellow when you mix these two together to create green dye.
Dye fabrics using more of the primary colors (red, yellow, and blue), because these will be the base for your other colors. They will also be good foundation colors which you will complement with secondary (purple, green, orange) and tertiary (brown, mauve) colors.
Decide which secondary colors to use according to the effect you want to create. Use a combination of opposites on the color wheel (e.g., red and green, blue and orange, yellow and purple) to complement each other in a contrasting and energizing way. Use colors close to each other on the wheel to create a general overall mood (such as green and blue for a calming effect, or red and orange for an energetic feel).
Use two-to-one or multiple combinations to tweak colors if you are mixing colors. For example, mix blue and red to create purple. However, if you want a deep violet or indigo, use more blue; increasing the red will create more of a maroon or mauve tone. Mix yellow and red to create orange, then mix with more yellow and some white for a nice golden color.