"The door of my house is white."
Translation:La puerta de mi casa es blanca.
'De color' is unnecessary. If you use the adjective blanca then you are obviously describing the color of something. You could use this structure sometimes, especially when your phrase is something like 'painted white.'
The biggest problem with your choice of words though is that your phrase uses 'white' as a noun (the name of a color is a noun). The adjective 'white' (blanco or blanca) matches the gender of the noun, but the name of the color is always blanco. Color names don't change for another noun's gender because color names are nouns. Nouns already have their own gender.
So- “La puerta es blanca."
But- “La puerta está pintada de blanco."