PIC 12F675 with wrong timing
I agree with your calculations and your code looks right. There may just be a couple of oversights resulting in your observations:


Timer1's red LED is alternated on overflow, so like TMR0, its period should be twice the overflow time of the timer: 2*18.18ms = 36.36ms.
That means the actual timings are both 17% faster than calculated, suggesting common cause.
The internal oscillator has a stated tolerance of 1%, though over temperature it can be 2% faster. That doesn't explain it.
But the oscillator does have configuration and calibration registers which could explain the discrepancy. In your preamble you specify the CONFIG setting of _INTRC_OSC_NOCLKOUT but is that sufficient to set it? I suggest changing to the INTOSC with CLKOUT, and measuring the CLKOUT pin. If it is not 4MHz as desired, look at adjusting the OSCCAL register. The Microchip document DS33023A may help here.