Much like Quiesce above me, I have found a transparency inconsistancy of the slider hit circles between the stable/beta patches and the Cutting-edge build. I do not know the cause for sure.
Reproduction:
In the Stable/Beta patch, a skin with a slider track override of [0,0,0] and a transparent hitcircle will show no colour difference between the normal hit circle and the slider hit circle when the background dim is set to 100%.
In the Cutting Edge patch, a skin with a slider track override of [0,0,0], (an invisible sliderendcircle) and a transparent hitcircle will show a colour difference between the normal hit circle and the slider hit circle when the background dim is set to 100% - most likely due to transparency. As Quiesce mentions, this looks a lot like the sliderhitcircle has had its transparency value doubled; or in other words the hitcircle is being placed ontop of itself twice.