Yellow adds brightness and a happy note to portraits. It is however not an easy color for portraits to use as a background. In its full saturation, yellow can seem to jump out of a photograph. A primal yellow may be too overwhelming for the person being represented. You can also read the full info here regarding color background photography.
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There are many shades of primal Yellow, ranging from a cool lemon yellow tone to a warm yellow shade. All shades convey vitality and joy. The intellect is associated with lemon yellow, while the creative and playful qualities of golden yellow are more strongly linked to yellow.
Both hues are highly active visually so accents should only be used in the background and the clothing of the subject. These accents will bring fun tonations to your portrait. Yellow accents will indicate that the person being depicted is active and inquisitive, with lively mental creativity.
Some shades of yellow may not be suitable for everyone. People with very dark hair will prefer the cooler shades of lemon yellow. People with ash brown or ash blonde hair colors will love the softer shades. The softer shades of golden yellow are ideal for natural redheads and people with reddish highlights.
Yellow is a great color to bring out the sunny side of a portrait. It can also be used to indicate a creative mind. Yellow is very active and requires some taming.