Frogs naturally vary in colour. While many of the frogs we see are green or brown, they can also be orange, red and yellow and they can sometimes have irregular dark blotches over their skin.
Frogs have the amazing ability to alter their skin colour to match their environment. During the breeding season, female frogs are often a pinky-red colour, whilst males get a blue tinge to their throat.
There are distinct markings to look for to be certain you have seen a common frog rather then something else. A frog will have a dark mask behind its eyes, stripy legs and paired folds of skin running along the back of its body.