How to use "regular expression" to separate specific strings in Oracle
Simple method:

col field1 format a6
col field2 format a6
col lvl format a3
variable B1 varchar2(32);
exec :B1 := '1:30,2:4,52:0,8:1';
select
  regexp_substr(regexp_substr(:B1, '[^,]+', 1, level), '[^:]+', 1) field1,
  regexp_substr(regexp_substr(:B1, '[^,]+', 1, level), '[^:]+', 2) field2, 
  level lvl from dual
connect by regexp_substr(:B1, '[^,]+', 1, level) is not null;

FIELD1 FIELD2 LVL
------ ------ ---
1      30       1
2      4        2
52     2        3
8      1        4


Or with fewer regexp_substr calls:

col field1 format a6
col field2 format a6
col lvl format a3
variable B1 varchar2(32);
exec :B1 := '1:30,2:4,52:0,8:1';
select
  regexp_substr(:B1, '[^:,]+', 1, level*2 - 1 ) field1,
  regexp_substr(:B1, '[^:,]+', 1, level*2) field2,
  level lvl from dual
connect by regexp_substr(:B1, '[^,]+', 1, level) is not null;

FIELD1 FIELD2 LVL
------ ------ ---
1      30       1
2      4        2
52     0        3
8      1        4