Here are some of my coloured zentangles done over the last 6 months. The challenge here is to use colours that do not clash, at the same time having enough contrast so that the patterns pop up. Some patterns are more delicate while others are bolder. Some are simple and others are more involved. The main thing is that I got a lot of fun from doing them and getting the pleasure of viewing a completed piece at the end.
Most zentangles took a few days to complete as I do not do one at one sitting. In terms of hours the smaller ones (the first 6 zentangle-inspired pieces) may take 8 to 12 hours, depending on the intricacy of the design.
The bigger zentangles (7 of them which measure about 13.5 inches in diameter) may take some 20 hours (give or take) depending on the speed with which I work, the intricacy of the design and the colouring process.
I use a lot of circles and dots as I like round shapes. You will find that a lot of the designs are influenced by flowers or leaves (as I am also a bonsai cultivator and love gardening). I also love textures and try to use different designs to bring about texture.
My preference for curves show a lot in these pieces. It lends a sense of movement and fluidity, compared to if I were to use straight lines to make the different segments. Most of the segments and designs are done spontaneously though sometimes I sort of plan the segments by working out a rough sketch before I actually do the piece.
Most of the designs are done freehand and spontaneously. With some designs I use a 2B pencil to work out the shape of the pattern before inking it.
Outlining some of the designs with a darker ink or even black helps to make the designs pop up.
Hope these thoughts that I am sharing here may be of some use to you when you do your own zentangles. Good luck.