I was trying to mix colors using the color slider and transparency:
The initial hex value is #BAB9B9 (R:186 G:185 B:185 A:1) , then I wanted to introduce some transparency; so, I moved the transparency slider to the left, but the color became (R:255 G:117 B: 117 A:0.9).
On R:255 G:0 and B:0, you can slide the transparency slider without problem. On other colors, as long as G and B is not 0, you get random changes with the transparency slider.