Value is the second dimension of color. Value distinguishes a light color from a dark one. By adding white to any color or mixing a primary of lighter color with it we create a color of higher value. Orange is actually a value of red because of the addition of yellow, a lighter color. Various tints of pink are values of red.
Chroma is the third dimension of color.
Chroma is the quality that distinguishes a strong, dark color from a weak one. Each of the three primary colors or hues are at their greatest chroma before the addition of tints of intermixing with other colors. They have not been weakened by the addition of white or black. Chroma is the intensity of a color. Thus a color in its greatest intensity is at its greatest chroma.