The gradient can't be seen as black

Quick answer：

Gradient colors can be designed in a way that they blend seamlessly into black, making them appear indistinguishable. This can be achieved through careful color blending and shading techniques in graphic design and printing. When a gradient transitions from a color to black, the transition can be so smooth that the eye perceives it as a solid black. This effect is often used in visual art and design to create depth or to create a sense of continuity.