You need to know the different associations of the colour red before using it in your photography. Knowing how it impacts the viewer can help you get more meaningful shots that your audience will love.
While we often think of love and romance, red can also trigger feelings of pain and anger. Blood is red and so it may evoke some emotions in connection with danger and violence. Saying that, it's often used in ceremonies and celebrations so this colour can also be a sign of status and royalty.
There are a myriad of shades, hues, and saturations of this colour, each of which can impact your audience quite differently. The impact of the colour red in photography is huge – far more than you initially imagine – it helps focus the viewer, it draws attention as well as adds depth of field if used correctly (I.e if red as a warm colour is used at the front with cooler colours at the back of the composition). Since the colour red attracts the viewer's eye, having multiple red objects can lead the viewer into the photograph - remember the eye will go to the largest red object first.
Thanks to red being the standard colour of traffic lights and stop/warning signals, our brains are inherently trained to notice the colour red first and it applies to photo compositions as well. Even if you have a different dominant colour in your photograph, a red element will catch the viewer’s attention and they will be drawn to that element first. Sometimes you may want this to be the case but sometimes you won’t so be careful when planning your composition.
Find something red in your home, backyard, or on the street – there should be no lack of ideas! You can experiment with photographing different red objects and think how it makes you/your viewer feels.