The non-waterproof strip in white color, while making into waterproof IP65 with surface covered by gel, will turn out more white than the non-waterproof strip. The color Kelvin looks go up.
To correct this problem, when order the waterproof strip, you can lessen the original color Kelvin need. For example, if you need waterproof IP65 strip in 3000K, you can ask for 2700K from the manufacturer directly. Or to avoid inconsistence when install the LED strip, by using strips from the same batch in the same space. By doing that, no reference, no difference exists.