If you're running low on gas, but in the high end of the gauge, that's clear at a glance based on the position of the needle within the colored section. This is

If you're running low on gas, but in the high end of the gauge, that's clear at a glance based on the position of the needle within the colored section. This is a much harder task with colored text. You can try using gradients to slowly fade to red, but interpolating colors is significantly harder than glancing at a gauge.