I use Japanese Masking Tape frequently in my altered book collage work, and have had questions about what it is and where to get it.
Japanese Masking Tape (also sometimes called washi tape) is printed in a range of colours and designs, comes in a range of widths, and is translucent (and repositionable), so is wonderful for collage work, both decorative and utilitarian.
I keep my selection on a stainless steel toilet roll holder. (I have another toilet roll holder to keep more utilitarian tapes like packing tape, duct tape, etc ... wonderful solution to collage supply chaos.)
A huge range available from PrettyTape on etsy [link]
Examples of masking tape in use: