Texture Painting - How to delimit the painting to the actual limit of the UV cells?

I am just getting familiar with Texture Painting. After doing some of it I see that after paiting one section, the neighbour section is affected. After a closer look I see that the problem seems to be that the paint goes beyond the actual UV cell borders

In the image above, the light green goes off the UV cell limits into the white.
Obviously the actual problem is when it goes into an adjacent cell that is supposed to be painted with a different color.

Is there a setting somewhere we’re supposed to check to avoid this?

Btw, the way I paint these sections is as follows:

  1. In Edit Mode, I select the faces I want to paint.
  2. In Texture P mode, I use the Fill brush, choose the color I want, click on the area I previously selected in Edit mode.
    Other than the problem I have now, it does a pretty good job.

Thanks guys,