"Rana arvalis" - the moor you know. Despite their name, they are found in a wide variety of habitats, ranging from forests to steppes to semi-desserts to even tundras. Normally they are reddish-brown in color, but males can turn a bluish hue (as pictured) for 2-3 days a year. (This usually happens after being rejected by a female, and is generally accompanied by the male curling up into a ball)
>But I lover her, my sweet Lenore