C# – RichTextBox specific colors per few characters / lines C#

This will work:

        // Create a temporary buffer - using a RichTextBox instead
        // of a string will keep the RTF formatted correctly
        using (RichTextBox buffer = new RichTextBox())
        {
            // Split the text into lines
            string[] lines = this.richTextBox1.Lines;
            int start = 0;

            // Iterate the lines
            foreach (string line in lines)
            {
                // Ignore empty lines
                if (line != String.Empty)
                {
                    // Find the start position of the current line
                    start = this.richTextBox1.Find(line, start, RichTextBoxFinds.None);

                    // Select the line (not including new line, paragraph etc)
                    this.richTextBox1.Select(start, line.Length);

                    // Append the selected RTF to the buffer
                    buffer.SelectedRtf = this.richTextBox1.SelectedRtf;

                    // Move the cursor to the end of the buffers text for the next append
                    buffer.Select(buffer.TextLength, 0);
                }
            }

            // Set the rtf of the original control
            this.richTextBox1.Rtf = buffer.Rtf;
        }

Android uses hexadecimal ARGB values, which are formatted as #AARRGGBB. That first pair of letters, the AA, represent the alpha channel. You must convert your decimal opacity values to a hexadecimal value. Here are the steps:

Alpha Hex Value Process

1. Take your opacity as a decimal value and multiply it by 255. So, if you have a block that is 50% opaque the decimal value would be .5. For example: .5 x 255 = 127.5
2. The fraction won't convert to hexadecimal, so you must round your number up or down to the nearest whole number. For example: 127.5 rounds up to 128; 55.25 rounds down to 55.
3. Enter your decimal value in a decimal-to-hexadecimal converter, like http://www.binaryhexconverter.com/decimal-to-hex-converter, and convert your values.
4. If you only get back a single value, prefix it with a zero. For example, if you're trying to get 5% opacity and you're going through this process, you'll end up with the hexadecimal value of D. Add a zero in front of it so it appears as 0D.

That's how you find the alpha channel value. I've taken the liberty to put together a list of values for you. Enjoy!

Hex Opacity Values

• 100% — FF
• 95% — F2
• 90% — E6
• 85% — D9
• 80% — CC
• 75% — BF
• 70% — B3
• 65% — A6
• 60% — 99
• 55% — 8C
• 50% — 80
• 45% — 73
• 40% — 66
• 35% — 59
• 30% — 4D
• 25% — 40
• 20% — 33
• 15% — 26
• 10% — 1A
• 5% — 0D
• 0% — 00