Page "ZX Spectrum" Paragraph 7

An " attribute " consists of a foreground and a background colour, a brightness level ( normal or bright ) and a flashing " flag " which, when set, causes the two colours to swap at regular intervals.

This scheme leads to what was dubbed colour clash or attribute clash, where a desired colour of a specific pixel could not necessary be accomplished.

This became a distinctive feature of the Spectrum, meaning programs, particularly games, had to be designed around this limitation.

Other machines available around the same time, for example the Amstrad CPC or the Commodore 64, did not suffer from this limitation.

The Commodore 64 used colour attributes in a similar way, but a special multicolour mode, hardware sprites and hardware scrolling were used to avoid attribute clash.