Here you can see two Hoya carnosa leaves.
Reasons for this difference: The Sun
Whit the sun: is smaller, more fleshy and lime green
Without the sun: is bigger, thinner and greener.
If it has dark green is probable that it will not flourish in a long time
the same for Krimson queen.
You can see hojas carnosas "diferencias"
Here is a link that might be useful: hojas carnosas