The answer is to buy colour printer, they aren't that dear. I print off A4 sheets of the 25k maps at 12500 scale using Memory Map. They are easier on the eyes at that scale. I keep the sheets in the plastic wallets used to keep documents in clip files. They fold easily into 4 to slip into a pocket. You can put in 2 sheets back to back and if need be, you can keep extra sheets between then, extracting and pocketing the used sheets as you go. The wallets are reasonably hard wearing and dirt cheap to replace.
As to apps, I use Memory Map, Garmin Basecamp, Google Earth and Viewranger. I usually carry the 25k map if the area I am in in my pack just in case, but I haven't ever pulled it out and used since I started printing off A4 sheets.