You can use the IsMatch function, which should do what you need. For example, if you want to highlight a text input that should contain an e-mail, you can use the following expression in its BorderColor property.
If(IsMatch(TextInput1.Text, Match.Email), Color.Blue, Color.Red)
The function IsMatch can be used for a lot of scenarios, but for simpler cases, like in your second example (minimum length), you can use the Len function, which returns the number of characters in a string. In an example similar to the one above, you could set the border color of the text input that is used to enter the telephone number to the expression below:
If(Len(TextInput2.Text) < 10, Color.Red, Color.Blue)