When I teach my children how to keep things organized and tidy, I let them know that everything has its place. See this pencil, where does it belong? Where does this sock go? Where do your books belong? As I list out these questions, they have a place for each item.
I can liken this idea to the principle of designated spaces in spirituality. Spirituality involves principles and this applies even to where we do and don't do certain things. A sacred space where you conduct your spiritual activities cannot be the same space that you eat, go to the bathroom or have sex. If spiritual activities are sacred and involve connecting with the pure and holy aspects of life, then we will have to ensure that we keep the space for those activities as clean and pure as possible. The pure and impure can't mix because purity is fragile.
The space where I do my prayers, connect with my Ancestors, meditate, leave food offerings, etc. is in an area where people don't walk. It is a space where shoes are not worn. It is a space where I do not go when I am angry or feeling negative. It is a space where I do not eat, drink, relieve myself of gases, curse, etc. It is a sacred space. I try hard to keep it clean and clear of any physical, mental, or spiritual waste and debris.
When I call upon my Ancestors, when I chant the names of Divinities, I want to give myself the best possible chance for them to hear me and come close to me to accept and grant my wishes. If there is dirtiness and filth, they will not come. They may not listen.
White is a favorable color to have in this space, as well as pictures of your Ancestors. In my spiritual journey I began with a basic sacred space and added things over time and continue to do so. The designated space is the number one priority in determining where your sacred space is. Even if it's the corner of a room, it can still suffice as your sacred space if it is kept clean and pure.