Hi Aura,
Many people like to have the colors of component in their computers match. Because of this many people choose to paint their components without realizing the effect in which this can have on the system cooling.
This first aspect to look at is the type of paint you are looking to use. Either way the coolers will need to have the current paint stripped and the next steps depend on the type of paint you're looking to use. In my opinion powder coating tends to look the best in computers and have minimum impact on the cooling efficiency of the computer however powder coating can be tricky to do.
In saying this though you will still want to think about the thermal headroom which you have. For example, do you have a fan pointed at the ram?
I would strongly recommend avoiding paints which are designed for cars as these tend to be capacitive and conductive. In conclusion you can paint the RAM coolers but if you do it incorrectly it will have an undesirable effect on the thermal efficiency.
To answer your other questions.
There is no real different between the 1866 MHz vs the 2400MHz and it would only really be noticeable in memory benchmarks.
I'm not entirely sure however I believe the heat spreader can be removed.
Don't hesitate to ask any other questions.
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