Hi Kate,
The Colour Blending option you can toggle On/Off is actually ‘Real Colour Blending’. When ‘On’ yellow + blue will give you green. Off and it will give you something “greyish” containing elements of both colours.
Either way any new paint will always blend with existing paint.
As an alternative to, or in addition to, using separate layers to avoid accidental mixing have you tried the Oils with “Instadry” turns On?
Bellow is a quick example of RCB On and with it Off.
I’m thinking you may have to get into more specific examples of what you are after with the pencil?
Perhaps a screenshot or two, say in PS and from AR so we can see what you have and what you are aiming for?
Maker Of Replica Macoys
Techie Stuff:
ArtRage 6.1.1 ~ 15" Macbook Pro ~ macOS 10.14.6 ~ 4 Core i7 3.1GHz CPU ~ 16GB RAM ~ Wacom Intuos4 M