Brushes keep on changing sizes/colours

Please post a screenshot including the Brushes Panel. 

The creator/s of the brush pack created the brushes that way for some reason. 

Maybe they wanted to create a kind of »set of colored crayons«, maybe something else, … 

In any case they created them that way and it’s up to you to change them to meet your actual needs. 

Being able to turn off some of the options for multiple brushes at once might be useful, feel free to post a Feature Request (mark it »Idea«, not »Discussion«). 

When a new brush is saved, there are options to use the size, the tool settings, and the color.

You could save a new version of the brush without those options selected. If you make changes to the brush size or color while that brush isn't selected, then you can go back to it, and it'll use the current color and size.

You can make a new brush preset by clicking the + at the bottom of either the Brushes (Window > Brushes) or Brush Settings (Window > Brushe Settings) panels or going to the panel menu (the hamburger menu in the upper right of a panel) for either of those panels.