A few parts to this.
The first is going to be getting the value from the database. Really not too much to work with on the specifics from your question, but from what I can tell is that you working with MS Access. This is a pretty generic sample as I know nothing about the tables or column names. What this will do is just get the value back from whatever instrument identifier you pass in. You will obviously need to change some values and possible types.
public Decimal GetInstrumentValue(int InstrumentID) {
string AccessConnection = "ACE12 connection string";
string AccessQuery = "SELECT Reading FROM Table WHERE Identifier = ?";
OleDbConnection conn = new OleDbConnection(_con)) {
OleDbCommand cmd = new OleDbCommand(AccessQuery, conn);
cmd.Parameters.AddWithValue("@Identifier", YourIdentifierValue);
conn.Open();
Decimal RetrievedValue = (Decimal)cmd.ExecuterScalar();
conn.Close();
}
}
Now for the coloring portion. The simple yellow-green-red with absolute thresholds is simple if-then logic
if (value < 0.5) set color to yellow
else if (value > 1.5) set color to red
else set color to green
Doing the gradual color change is going to be a little more complicated without a million if-then lines.