Low key-of reduced intensity; restrained; understated.having chiefly dark tones, usually with little tonal contrast .
Dictionary.com

-When something is less vibrant or grasping

high key-having chiefly light tones, usually with little tonal contrast.

Dictionary.com

-Making something pop over the other tones in the project.

texture density-It also involves groups of objects appearing denser as they move farther away. Also could be explained by noticing a certain amount of detail depending on how close something is, giving a sense of depth perception.

wikipedia

– the way something looks more detailed then another objective giving it a sense of space in relation to its focus.

gouache-a method of painting using opaque pigments ground in water and thickened with a gluelike substance

– changing the texture of the paint to make it look darker and thicker.

Tonal progression-is a succession of color mixtures proceeding from dark to light. In addition to value change

Theryderstudio.com

-The more color you add changing it to different lightness or darkness.

shade- a color, especially with regard to how light or dark it is or as distinguished from one nearly like it.

Google.com

-How light or dark something is

tint-  various lighter or darker shades of a color.

Merriam-webster.com

-how the shades look lighter or darker

tone- in an artistic context refers to the light and dark values used to render a realistic object, or to create an abstract composition.

wikipedia

-how lightness and darkness make art realistic. 

venn diagram-uses circles to represent sets, in which the relations between the sets are indicated by the arrangement of the circles.

Dictionary.com

– The way colors over lap when they combine