|The 'waves' you're seeing are where different (bright) colours cause cross-colour noise, where the colour signal interferes with the luminance signal. This problem is inherent in composite video signals - you don't normally see them on TV programs as intense colour changes are suppressed before transmission.|
S-Video doesn't suffer from this because the two signals (chrominance and luminance) are transmitted separately.
The best way to reduce the problem is to experiment with different colours when placed side by side - in general bright red & bright blue next to each other (eg. at the edge of a letter) produce the worst results. Use lighter (paler) colours and place dark text (Eg. red or blue) on a bright background (eg. yellow or white) and vice-versa - this makes the luminance change more prominent and therefore less susceptible to the colour 'noise' that gets mixed with it to form the composite video signal.