Many box dyes are around 10 volume.
20 volume peroxide is the correct strength to open up the hair shaft to accept colour for grey coverage, and is often more effective at grey coverage than something less, like 10 volume. That said, if you are just depositing colour and don't require any lift, 10 volume is often sufficient unless you are hitting the 50% grey type ratios. Many will find 20 volume more competent and this kind of coverage though, particularly with deeper bases.
In terms of "Winter" colours you are looking for cool to neutral tones. For this you can refer to the International Colour numbering system.
You know how a lot of dyes, including box dyes, have numbers as well as names? The names mean nothing..."Haviana" "St Tropez" etc although others mean something like "Iced chocolate" or "Cinnamon" but are not exactly accurate in terms of what they contain. The numbers decode it.
The first number refers to depth. The OP should avoid anything below a 5 if she doesn't want to get too dark and get too much colour build up. 5 is a mid brown. 6 is a dark blonde (though most would still consider this light brown to look at - a lot of primary aged kids have this colour, a kind of beige head that isn't quite blonde and isn't quite brown - "bronde". Lol). Level 7 is still quite a deep blonde, but lighter than a 6, 8 is getting to proper blondness by most people's standards, and level 9 and 10 are your light blondes.
The second 2 colours refer to tone. 1 is green ash. 2 is violet ash. 3 is gold. 4 is copper. 5 is mahogany (which may seem warm but is technically classed as cool). 6 is red.
The OP should avoid any of the warm colours, and as a winter, also avoid mahogany if she is looking for a cool or neutral brown. A little bit of gold is fine, but she should pair this up with a violet ash for an iced or "iridecent" effect. If she is struggling with her hair being a warm base from bleaching or if her hair is throwing out rusty tones from the lightening, then green and violet ash with counter this. Violet kills gold tones, and green ash kills copper tones.
Dont be too scared of something with a gold reflect as this coupled with a base 5 tends to give a pleasing chocolate colour which suits most skin tones. Avoid copper like the plague.
A 5.23 or a 5.21 or a 5.02 or something would be idea. I will try to link to such products in a sec, both professional and box dyes. If you use a box dye squirt it into a dish and apply with a tinting brush if you have managed to fix your build up issue and don't want to end up back there. Back in a tick with some links.