Bleed definitely happens with blue too but since solid blue chrominance is less common in graphics (graphics tend to use brighter sky/azure/royal blue) whereas

Bleed definitely happens with blue too but since solid blue chrominance is less common in graphics (graphics tend to use brighter sky/azure/royal blue) whereas solid red is quite common. But bleed won't happen with green because green is basically the luminance channel in YCbCr/YUV. This means that green runs at full sample resolution compared to red and blue which run at 50% to 25% resolution (depending on subsampling).