Sometimes picture when you want to blend them together have a different kind of tone.
Like this picture.

The background is warm colored but the person is cold toned. And you see that it doesn't blend well. I advice you to play with these things until you see that it matches.

Saturation:
Saturation describes the intensity of the colour. And lightness refers to how light or dark the colour is. A grayscale or black-and-white photo has no colour saturation, while a full-colour photo of a field of sunlit wildflowers might be extremely saturated.

White balans
The white balance function of a digital camera usually ensures the objects are captured in the correct colors in correlation to the light source. Normally white balance is automatically adjusted depending on the light source correlated color temperature. I used it for the skin mostly of the time.

Correction of gamma
Gamma correction is a technique used to display colors on your screen accurately. It adjusts for a device's non-linear display characteristics, ensuring the encoded and decoded luminance in digital images and videos is accurate.

And voila if you played with it well you get this.

Queries about warm and cold tones? >>>>