Hi, thank you for your questions.

1) arbitrage and xarbitrage are almost the same except that xarbitrage allows to make a cross currency comparison and make some filtering and apply custom currency exchange rate to play with the data a bit.

2) in your screen shot we consider profitability as if you buy and sell 10 BTC equal lots to close the operation.

the number in larger font means percentage of arbitrage and in smaller font it currency equivalent.
21.45% = 631.4 USD

sign means + profit or - loss.

As far as I can remember white color is for loss greater than 10%
yellow color is when loss is between -10% and 0%
and orange is for profit

hope I have answered your questions. If you have more questions we will be glad to help.