Color gradient from green to red, any adjacent colors being indistinguishable for the human eye
<a href="//commons.wikimedia.org/wiki/User:Hyacinth" title="User:Hyacinth">Hyacinth</a>
<a href="//commons.wikimedia.org/wiki/File:Color_gradient_illustrating_a_sorites_paradox.png" title="File:Color gradient illustrating a sorites paradox.png">File:Color gradient illustrating a sorites paradox.png</a>