Yes, you'll have much heartier flowers but your stems and leaves will be weak.

If you vegitate your plant with the wrong kelvin it will not produce as potent of a flower as it would if you cycled the kelvins throughout the different stages of growth.

Truthfully, to achieve the highest potency possible, you should try to use as much of BOTH warm and cool kelvin lighting throughout the plants WHOLE growth. This will ensure full spectrum photosynthesizing which will in fact increase the initial THC potency throughout the whole plant when flowering begins.

So personally, I'de go with your original plan to have both spectrums on the plant the whole time. This of course depends on the kelvin rating of those lamps. If they are not extreme it wont work like you want it to. In which case you would be better off with one or the other and not both.

Now if you can afford it, you can't go wrong with having two of the blue spectrum and two of the red.

Here's a little information on Kelvin for you, from what I know:

Kelvin temperature is a numerical measurement that describes the color appearance of the light produced by a lamp and the color appearance of the lamp itself, expressed on the Kelvin (K) scale.

The science behind determining color temperature values starts with the theoretical black body radiator, a block of black metal through which electric current is passed (performed as a computer model). As the metal is heated, it turns red-yellow, then white, then blue; as the temperature of the metal is measured at any given color produced, we then match the color to that temperature and a color temperature value is determined.

Ok so how does this apply to lighting?

Well, the Kelvin temperature of lamps is used to categorize them as warm, neutral or cool sources. The terms are not directly related to temperature; instead, they describe how the light source appears visually.

Warm sources actually have a lower color temperature (3500K or less), producing a red-yellow appearance. Neutral sources (between 3500K and 4100K) tend to have a yellow appearance. A lamp with a color temperature of 5000K is considered pure white light (Full Spectrum) with the lamp becoming more blue in color as the color temperature is increased.

Now Cannabis will survive in a pretty wide range of Kelvin. However, to achieve maximum photosynthesizing it's best to focus on the Kelvin range that is used most by the plant to utilize your light more efficiently.

Which Kelvin range promotes the most efficient photosynthesis energy is debateable but here is a general idea of how it works:

5K - 7K Kelvin:
Promotes bushy growth. Ideal for rapid growth phase of plants.
Greatly enhances all-around plant growth when used with super
high output, high pressure sodium or 3K warm metal halide lamps.

4.2K - 4200 Kelvin:
Can be used as supplimental blue lighting when used with a 3K
source.

4K - 4000 Kelvin:
Best single source for plant growth, producing shorter, bushier
growth than 3700 Kelvin and color rendition. Used in general
plant lighting.

3.7K - 3700 Kelvin:
This coated lamp is used in general plant lighting and for more
rapid growth than 4000 Kelvin produces.

3K - 3200 Kelvin:
Highest photosynthetically active radiation (PAR) value of all HID
lighting for all phases of plant growth. PAR watts account for the
nutritional value of light and are a direct measure of the light
energy available for photosythesis.

2.7K - 2700 Kelvin:
Redder color mix, used for propagation, blooming, supplemental
greenhouse lighting.