Font and control size matter
Use color wisely
Consider multi-lingual requirements
Relevant: Closely connected or appropriate to what is being done or considered./ˈrɛləv(ə)nt/
Font and control size
Fonts are very important because text automatically attracts attention the font size, colour and case will all give the users clues to the meaning and relevance of the text before the user reads the text.
Use colour wisely
Use it wisely but do not rely on it.
Red is natures warning colour, yellow is great for getting attention without necessarily implying danger, grey means not so important.