Synthetic dyes are widely used in the food industry to maintain or restore the colour of food during processing or storage, the azo ones occupying the first place in terms of the extent of use. Compared to dyes obtained from natural sources, synthetic ones present relevant advantages, such as higher stability and lower cost. Despite these advantages, their use has been linked to side effects, such as allergic reactions, carcinogenic effects, behavioural and neurocognitive effects, but also medium and long-term toxicity. In this context, this review describes the most used yellow and red synthetic dyes, namely Tartrazine, Quinoline Yellow, Sunset Yellow FCF, Carmoisine/Azorubine, Amaranth, Ponceau 4R, Allura Red AC, as well as their applications in food products. Moreover, it aims to provide current data on the toxicity issues and the possible negative effects on children's behaviour of these dyes, based on the evaluations previously carried out by European Food Safety Authority (EFSA), but also on subsequent studies available in the literature.