One of the most challenging aspects of this kind of work is getting the base coat of paint the right color. If the base coat of paint is not right then you will never get the new work to match the existing wood grain coloring.
So what I do is try to determine the color to use by looking for the light areas in the wood grain and imagining what color I could use based on that. I have to keep in mind that I will be going over it with layers of different color browns so I can't just use the color I see but I have to determine when the color is painted over how it will match up.
You can see in the first photo the arrows indicate where I was looking at to figure out what base coat to use. Then as you can see I painted the side fillers that color, the wood there was already primed white when I arrived.
In the next photo I have applied the first layer of wood grain color.
In the next photo I am getting closer by adding more layers of different wood grain color.
The photo below shows the completed project. I pretty much was able to nail it.
Another angle showing how now the vanity looks like it is all one piece as if it came like that.
By the way here is view from the balcony patio. The crystal clear waters of the Gulf of Mexico. That is looking west so you get some great sunsets sitting out on the patio.