Aprende los colores en español con ejemplos simples

Why does “rojo” become “roja” in Spanish?

In Spanish a color is not one fixed word. It changes its ending to match the thing it describes. A masculine noun takes the -o form, and a feminine noun takes the -a form. So the tomato is rojo but the apple is roja: el tomate es rojo, la manzana es roja. Same color, two endings. This matching happens with most descriptive words, not only colors.

The clip shows the pattern cleanly: la nieve es blanca but el auto es blanco; la gata es negra but el gato es negro. Note that some colors never change, like azul (blue) and verde (green): el cielo es azul, la bicicleta es azul.