Why on weather surface charts high pressure is blue and low pressure is red?
Red/blue for pressure is in no relation to surface temperature. Storms develop where the pressure is very low. Red being associated with danger is a good color choice for low pressure.


  Storms are created when a center of low pressure develops with a system of high pressure surrounding it.


Low pressure is also associated with decreased aircraft performance, both lift and engine power. See below and find the strongest storm system.

(Source)



Blue for cold and red for hot is used for coloring the weather fronts:

(Source) 1. cold front 2. warm front 3. stationary front.