On planned pooling: Unskein your yarn and lay it onto the floor in a zig-zag pattern, so that the colours align. Then mark the first 3-4 “corners”. Each of those rows of yarn is one row of knitting. Cast on using a backwards loop cast-on. Turn when you reach the corner. Knit the second “row” and If you use up yarn before you hit the colour match from the cast-on row, switch to a smaller needle. If your colour match is moving ahead of the previous row, switch to a larger needle.
Free Rainbow Scarf by Eline Sanders, knit by eline. The recipe includes a chart on how to make the pattern showed in the pictures, but double knitting is by nature very easily adoptable to any pattern that may strike your fancy.