I’m struggling to find a matching blue colour for this red one I’ve got:
By ‘matching’ I mean similar feel, in terms of brightness, contrast, lighting etc…
I’m new to graphic design so I don’t really know how to find similar colours.
There are some “rules” regarding color harmonies that you will find very helpful for this case and any future ones you might have regarding colors.
Color combination is really the most important part of color theory
and designing with colors, and also the hardest– It always comes down
to your personal judgement and how you look at colors. There are,
however, some guidelines that can be used to make a color combination
that is interesting and pleasing to the eye. (source)
Colors that are opposite each other on the color wheel are considered to be complementary colors (example: red and green). The high contrast of complementary colors creates a vibrant look especially when used at full saturation.
Analogous color schemes use colors that are next to each other on the color wheel. They usually match well and create serene and comfortable designs. Analogous color schemes are often found in nature and are harmonious and pleasing to the eye.
A triadic color scheme uses colors that are evenly spaced around the color wheel. Triadic color harmonies tend to be quite vibrant, even if you use pale or unsaturated versions of your hues.
The split-complementary color scheme is a variation of the complementary color scheme. In addition to the base color, it uses the two colors adjacent to its complement. This color scheme has the same strong visual contrast as the complementary color scheme, but has less tension.
The rectangle or tetradic color scheme uses four colors arranged into two complementary pairs. This rich color scheme offers plenty of possibilities for variation. The tetradic color scheme works best if you let one color be dominant.
You can use an online service like Kuler to calculate these.