Colors only shown... sometimes?

[boriel]

The thing here is that you're using print64, which "simulates" 64 columns, but this is not real. The ZX Spectrum hardware still uses 32 columns (for attributes). So if you change an ATTR color on an even column (0, 2, 4...) and print something, and change again the color for an odd column, the attr will be overwritten every time by the odd column.