termcol: avoid hexadecimal conversion for newyuv colours Simplify default initialiser; previous version available as newyuv8().
termcol: hsv method in Colour module
termcol: list 256-colour hues starting with red Most wheels have red at 0° so having it on top is more familiar. Coincidentally also avoids undesirable row breaks.
termcol: lay out 256-colour table by h/s/v
termcol: 16-colour palettes for msx and c64 Additional data for common '90s home computers from Wikipedia <https://en.wikipedia.org?oldid=686243993>, with composite YPrPb values converted to hex and to RGB using formula from <https://en.wikipedia.org?oldid=670394866#ITU-R_BT.601_conversion>.
termcol: globally define luma coefficients Prepare for reuse in other YUVish conversions.
termcol: colour class to facilitate calculation and formatting