You just can't expect to be able to make pale beers with a kettle on a gas flame. To see what is happening I suggest that you with hold a bit of the grist. Now complete your mash schedule and before continuing on with the boil take that with held grist portion, mix it with water and compare its color side by side with some of the mash. This will show you how much color was developed during the mash. Now, before adding heat for the boil, withdraw a bit of the wort and hold it aside while you go ahead with the boil in the kettle. At the conclusion of the boil again pull out a bit of the wort and compare it side by side with the wort you held back. This will show you how much color was developed in the kettle.
This should show you where the color is coming from but it won't help you to figure out what to do about it. You could add some metabite to the wort sample to see how much it reduces color but you are really only likely to succeed if you completely change your mashing/boiling processes.
