If memory serves me correctly, and as it’s an analogue format, it can’t really be described as either. However the luminance is layed in one stripe whereas the colour components are time compressed into a single stripe giving the effect of compression but it is only in the time domain and is stretched back on playback.
But as in almost all tape formats the colour information is sampled (analogue) at half the rate of the luminance ie, 13.5MHz for the luminance and ~6MHz for each of the colour components.