Assuming you have made your icons in the colour that you wanted them to be (in photoshop or sketch or whatever), you can do this via the attributes inspector.
Go to your storyboard, find your view controller (whcih should have been embedded in the tab bar controller already) and select the tab bar at the bottom of the view controller.
In the attributes inspector set the "Image" under Bar Item to your unselected tab bar item image (which should be in your assets already) and set the "Selected Image" under Tab Bar Item to your selected version.
Next, go to your asset catalogue, select your image and in the attributes inspector, under Image Set, set the Render As to Original Image. Do this for all your icons.
This should now work