The most common flaw in a site built without a designer is not that the colours are ugly — it is that they are different on every page. The button on the home page is a slightly different green from the one on the service page, and heading sizes drift from screen to screen.
The cause is not taste but making the decision repeatedly. Open a colour picker every time you build a page and you will get a slightly different value every time. The fix is to decide once and store it in one place.
Five colours are enough
You do not need a broad palette. Five colours with defined roles will carry an entire business site.
Check the contrast while you are here. Pale grey text looks refined on your monitor and disappears on a phone in daylight. The accessibility guidelines (WCAG) recommend a contrast ratio of at least 4.5:1 between body text and its background, and any free contrast checker will judge two colours instantly.
This is not only a matter of courtesy. Copy that cannot be read converts nobody, however well it was written.
One or two typefaces, no more
The safest arrangement is one typeface for both headings and body, distinguished only by weight. If you want two, stop at one for headings and one for body. Past three the page turns noisy and, more importantly, there are more font files to download before the first screen appears.
Non-Latin webfonts are considerably larger than Latin ones, which makes loading every available weight an expensive habit. Load only the weights you actually use.
Store them once and rebranding takes minutes
Where you store colours and fonts decides what the next change costs.
Brand colours do change as a business grows: a logo gets refined, print and screen have to match, a name changes. A site with global settings needs one value edited; a site coloured page by page needs all of it edited.
How far theme settings can take you is covered further in the Themes & plugins archive, and if font loading is slowing down your first screen, that gets handled as part of our optimization program.
Next part
With colour and type settled, screen size is next. The following part is about mobile — what you miss by only ever checking on a desktop.